Multiple plane bar code reader for reading optically encoded data

ABSTRACT

A bar code reader having two reading windows, i.e., a bottom window and a side window. An increased number of scanning lines are used for constituting scanning patterns for scanning bar codes, and the arrangement of the optical system is contrived to decrease the whole size of the bar code reader and, particularly, to decrease the depth of the bar code reader. A source of laser light, a splitter for splitting the laser beam emitted from the laser light source into two, a reflection mirror for transmitting one beam from the splitter to a polygon mirror, the polygon mirror which rotates to scan the incident laser beam, a mirror system for emitting the beam reflected by the polygon mirror through the reading window, and a focusing member for focusing the beam reflected by the bar code onto a detector that detects the beam reflected by the bar code, are arranged on the same line in the bar code reader. By using a concave mirror, furthermore, the beam reflected by the bar code is folded back to one detector. The light-receiving surface of another detector is faced downward to receive the beam reflected by the bar code through Fresnel lens and mirror, thereby to decrease the depth of the bar code reader. Furthermore, the beam passage from the reflection mirror goes through the lower surface of the polygon mirror intersecting the axis of rotation of the polygon mirror.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a bar code reader and, moreparticularly, to a bar code reader used for a POS (point-of-sale) systemwhich is installed on a counter of a store and is used for reading barcodes are attached to goods.

2. Description of the Related Art

In POS systems and in physical distribution systems, so far, it has beenis a widely accepted practice to exactly calculate and manage goods byreading bar codes. The bar codes are attached to the goods and are readby using a bar code reader.

In such a bar code reader, a ray of light such as laser light is emittedonto the bar code, which is attached to the article by printing or thelike method. Thus the bar code reader scans the bar code surface, andthe laser light reflected by the bar code is detected to read the barcode.

FIG. 1A is a diagram illustrating a conventional bar code reader in aperspective manner so that the internal structure can be seen. The barcode reader employs a source of laser light, such as a semiconductorlaser, as a source of light. In FIG. 1A, reference numeral 201 denotes alaser module constituted by a laser beam source and lenses. Referencenumeral 202 is a polygon mirror which is a polyhedral mirror, having aplurality of reflection planes. The polygon mirror 202 is rotated by amotor 207. The laser beam emitted from the laser module 201 is reflectedby a small plane mirror provided at the center of a concave mirror 203and arrives at the reflection plane of the polygon mirror 202. The laserbeam is reflected by the reflection plane of the polygon mirror 202.Here, however, since the polygon mirror 202 is rotating, the laser beamis scanned, for example, in the clockwise direction in the drawing.

Reference numeral 204 denotes mirrors for splitting the scanning lineand on which is incident the laser beam scanned by the polygon mirror202. The laser beam is downwardly reflected by the scanningline-splitting mirrors 204, upwardly reflected by a bottom mirror 205 ofnearly a V-shape, and is emitted through a reading window 206.

The laser beam emitted from the reading window 206 scans the articlethat passes over the bar code reader. The laser beam, after havingscanned the article, is reflected by the surface of the article to whichthe bar code is attached, and is caused to be incident on the bar codereader through the reading window 206.

Light reflected by the bar code of the article and incident on the barcode reader, is reflected by the bottom mirror 205, scanningline-splitting mirrors 204 and polygon mirror 202, and is caused to beincident on the concave mirror 203. The concave mirror 203 focuses thelaser beam reflected and diffused by the bar code toward a lightdetector 208. The laser beam received by the light detector 208 isdecoded by a decoding circuit in the bar code reader and is output to anexternal unit.

The bar code reader shown in FIG. 1A has only one reading window 206.Such a bar code reader can be installed on an accounting counter in astore in two ways. i.e., the bar code reader is installed so that thereading window 206 is in flush with the surface of the accountingcounter, or the bar code reader is so installed that the reading window206 is nearly vertical to the surface of the accounting counter.

When the bar code reader of FIG. 1A is installed on the accountingcounter, there is offered only one reading window 206 as describedabove. When the article is passed over the bar code reader at theaccounting counter to read the bar code attached to the article, the barcode is not scanned by the scanning light unless the bar code faces thereading window 206, and the bar code is otherwise not read out. This isbecause in conventional bar code readers, a limitation is imposed on therange scanned by the scanning light or on the direction in which thescanning light is emitted.

To solve the above problem, a bar code reader has in recent years beendevised having a plurality of reading windows. Such a bar code readeremits the scanning light through the respective reading windows to scanthe article having bar code from a plurality of different directions.

FIGS. 1B and 1D illustrate appearances of the bar code readers 210 and220 in which the above-mentioned countermeasure is taken. These bar codereaders 210 and 220 are provided with reading windows (hereinafterreferred to as bottom windows) 216, 226 formed in the bottom surface ofthe device, and reading windows (hereinafter referred to as sidewindows) 217, 227 formed in the side surface erected at an angle nearlyvertical to the bottom windows 216, 226. Scanning light is emitted fromthe bottom windows 216, 226 toward the upper side windows 217, 227. Onthe other hand, scanning light is emitted in nearly the horizontaldirection (toward the operator) from the side windows 217, 227.

As shown in FIGS. 1C and 1E, the difference between the bar code readers210 and 220 is that the bottom window 216 of the bar code reader 210 hasa size of 5 inches×4 inches, whereas the bottom window 226 of the barcode reader 220 is of a trapezoidal shape having a size of 6 inches×6inches.

As described above, a plurality of reading windows are provided, and thescanning light is emitted in a plurality of directions through therespective reading windows. Therefore, the article 209 passing on thebar code readers 210, 220 is irradiated with scanning light from aplurality of directions, and the probability for scanning the bar codeis enhanced compared with when a bar code reader having only one readingwindow is used.

FIG. 1F illustrates a calculation counter (check-out counter) 230 onwhich the above-mentioned bar code reader 220 is installed. On thecheck-out counter 230 is installed the bar code reader 220. The operatorP stands at a position facing the side window 227.

On the upper side of the side window 227 is provided a key board 222 forinputting data related to the goods to which no bar code has beenattached. A belt conveyer 233 exists on the upstream side of thecheck-out counter 230 to carry the goods to the position of the bar codereader 220. Reference numeral 235 denotes a guide plate for guiding thegoods onto the bottom window 226 of the bar code reader 220.

As the article is carried to the position of the bar code reader 220 andpasses by the bar code reader 220, the bar code is read out irrespectiveof the direction of the bar code attached to the article. A POS terminal234 is provided by the side of the operator P, and the calculationprocessing is executed by the POS terminal 234.

FIG. 1G illustrates a bar code readable area of the bar code readers 210and 220 of FIGS. 1B and 1D. Here, the hatched region RP represents theregion where the scanning beams emitted from the side windows 217, 227and the bottom windows 216, 226 are focused. In This the region, barcode is read out even when the bar code is turned in the horizontaldirection by 360 degrees. Thus, since the scanning beams are emittedfrom the two reading windows, the bar code readable area is broadened.Besides, even when the bar code surface does not completely face to onereading window, the bar code can be read out.

However, even such bar code readers have problems as described below. Inthe case of the bar code reader 210 shown in FIGS. 1B and 1C, forexample, the bottom window 216 has a size of 4 inches×5 inches. Thus,the bar code reader 210 shown in FIGS. 1B and 1C has a narrow bottomwindow 216, and a pattern (hereinafter referred to as scanning pattern)is constituted by a small number of scanning lines emitted from thebottom window 216.

In the case of the bar code reader 220 shown in FIGS. 1D and 1E,furthermore, the bottom window 226 has a size of 6 inches×6 inches,which is larger than the size of the bottom window 216 of the bar codereader 210 shown in FIGS. 1B and 1C. However, the bottom windows 216,226 are usually constituted by a reinforced glass which resists fallingarticles, and are, hence, expensive. Therefore, the bar code reader 220of Figs. 1D and 1E becomes expensive.

Various optical systems are arranged in a bar code reader, and thearrangement must be so contrived that the reader does not become bulky.However, in the conventional bar code readers and, particularly, in thebar code readers 210, 220 which read the bar code through two surfaces(i.e., through the bottom windows 216, 226 and the side windows 217,227), a total of two laser beam sources are provided: a laser beamsource for the bottom windows 216, 226 and another laser beam source forthe side windows 217, 227. Therefore, arrangement of the optical systemsfor accomplishing a desirable reading ability involves variouslimitations and problems, resulting in an increase in the size of thedevice and an increase in the cost of production.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a bar codes reader forreading bar code using a bottom window and a side window, wherein onlyone source of light is employed to emit laser beam from the bottomwindow or the side window. The arrangement of the optical systems in thebar code reader is so contrived that the device will not bulky, and thedevice is fabricated at a reduced cost. Another object of the presentinvention is to read the bar code attached to an article maintaining animproved precision by increasing the number of scanning patterns emittedfrom the bottom window.

According to the present invention, in particular, it is possible toincrease the number of scanning lines for constituting a scanningpattern emitted from the bottom window compared with that of theconventional devices. This is accomplished by the arrangement of mirrorsfor forming scanning patterns.

According to the present invention, furthermore, the external size ofthe device and, particularly, the depth can be decreased compared withthe conventional devices. This makes it possible to install the readereven on a narrow accounting counter.

In the present invention, a source of light, scanning means, focusingmeans and the like constituting an optical system are arranged on thecenter line of the device (i.e.) in a specified plane, so as to sharethe same optical axis. In particular, the ray of light guided by thereflector is caused to intersect the axis of rotation of the scanningmeans, since the axis of station is included in the specified plane.Therefore, no extra space needs be formed in the reader for conductingthe ray of light, and the device can be realized in a small size.Moreover, the ray of light conducted by the reflection mirror is allowedto pass under the scanning means, making it possible to decrease theheight of the device.

The light detector is so disposed on the bottom surface of a bottomscanner portion that the light-receiving surface is faced in thehorizontal direction and is so disposed in the side scanner portion thatthe light-receiving surface is faced downwards, in order to effectivelyutilize space in the device. In this case, the light detector does notintercept the passage of rays of light such as scanning lines.Accordingly, limitation on the length of the scanning lines, on thedirection and on the angle can be decreased to realize a scanningpattern for reading the bar code more efficiently.

In the present invention, furthermore, the frame of the bottom scannerunit is divided into upper and lower portions, and the mirrors forforming the scanning patterns are mounted on the inside of the frame.Therefore, no additional mechanism is necessary for arranging themirrors in space inside the device; i.e., space in the device iseffectively utilized.

Moreover, since the depth of the bottom window is increased comparedwith the conventional bar code readers, the area for reading bar codescan be broadened compared with that of the conventional devices, and itbecomes more probable that the bar code can be read compared to theconventional devices.

To focus light reflected by the bar code and guided to the detector,furthermore, the optical passage of the reflected beam is folded byusing a concave mirror, making it possible to shorten the length of thepassage of the reflected beam.

According to the present invention, furthermore, the beam diameter of asemiconductor laser of either the vertical direction or the horizontaldirection is changed by using a rectangular prism, but the other beamdiameter is not changed; i.e., the beam diameters are set to be nearlythe same in both the horizontal direction and the vertical direction.According to this constitution, the laser beam is less intercepted(squeezed) by, for example, an aperture, and the diameter of the laserbeam is not deformed.

In particular, use of the rectangular prism makes it possible to reducethe size of the laser module.

With the source of laser beam, means for changing the beam diameter andmeans for splitting the beam being contained in a module, furthermore,there is no need to bring the optical axes of each of the portions intoalignment.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more clearly understood from thedescription as set forth below with reference to the accompanyingdrawings, wherein:

FIG. 1A is a perspective view illustrating the internal constitution ofa conventional bar code reader;

FIG. 1B is a perspective view illustrating the appearance of aconventional bar code reader having two reading windows;

FIG. 1C is a diagram illustrating the size of a bottom window of FIG.1B;

FIG. 1D is a perspective view illustrating appearance of anotherconventional bar code reader having two reading windows;

FIG. 1E is a diagram illustrating the size of a bottom window of FIG.1D;

FIG. 1F is a plan view illustrating an accounting counter incorporatingthe bar code reader of FIG. 1D;

FIG. 1G is a diagram illustrating a bar code readable area of theconventional bar code reader having two reading windows;

FIG. 2A is a perspective view illustrating the appearance of a bar codereader according to an embodiment of the present invention;

FIG. 2B is a perspective view illustrating a state where the bar codereader of FIG. 2A is installed on an accounting counter;

FIG. 3 is a side sectional view schematically illustrating the internalconstitution of the bar code reader of FIG. 2A;

FIG. 4 is a diagram illustrating a bar code readable area by the barcode reader of FIG. 2A;

FIG. 5A is a front view illustrating an outer size of the bar codereader of FIG. 2A;

FIG. 5B is a side view illustrating an outer size of the bar code readerof FIG. 2A;

FIG. 6 is a block diagram illustrating an optical system of the bar codereader of FIG. 2A;

FIG. 7 is a perspective view illustrating a state of when a cover isremoved from a bottom scanner portion of the bar code reader of FIG. 2A;

FIG. 8A is a plan view of the bar code reader of FIG. 7;

FIG. 8B is a side view of the bar code reader of FIG. 7;

FIG. 9 is a perspective view illustrating the internal constitution of alower frame of the bar code reader of FIG. 7;

FIG. 10A is a plan view of the lower frame of FIG. 9;

FIG. 10B is a plan view illustrating the constitution of the lower frameof FIG. 9 according to a modified embodiment;

FIG. 11 is a side sectional view of the lower frame of FIG. 10A;

FIG. 12 is a perspective view of a state where the upper frame and thelower frame are removed from the bar code reader of FIG. 7;

FIG. 13A is a plan view of a mirror frame shown in FIGS. 8A and 8B;

FIG. 13B is a front view of the mirror frame shown in FIGS. 8A and 8B;

FIG. 13C is a bottom view of the mirror frame shown in FIGS. 8A and 8B;

FIG. 13D is a side view of the mirror frame shown in FIGS. 8A and 8B;

FIG. 14 is a perspective view of an assembly illustrating theconstitution of the mirror mounted on the mirror frame;

FIG. 15 is a side sectional view illustrating the constitution of aninternal optical system of the bar code reader of FIG. 7;

FIG. 16 is a block diagram illustrating the passages of scanning beamsinside the bottom scanner portion;

FIG. 17 is a block diagram illustrating the passages of scanning beamsinside the side scanner portion;

FIG. 18 is a diagram illustrating scanning patterns reflected by oneplane of a polygon mirror and is emitted through the bottom window;

FIG. 19 is a diagram illustrating the whole scanning patterns emittedthrough the bottom window;

FIG. 20 is a diagram illustrating the whole scanning patterns emittedthrough the side window;

FIGS. 21A to 21C are diagrams illustrating some of the scanning patternsemitted through the bottom window;

FIG. 21D is a diagram illustrating some of the scanning patterns emittedthrough the side window 4;

FIG. 22 is a diagram illustrating the passages of rays of light fromwhen a laser beam emitted from a VLD module is reflected by the polygonmirror until when it is emitted through the bottom window and the sidewindow;

FIG. 23 is a perspective view illustrating the passages of rays of lightuntil the laser beam emitted from the VLD module is reflected by thepolygon mirror;

FIG. 24 is a diagram illustrating scanning patterns of scanning beamsemitted from the bottom window of FIG. 1C;

FIG. 25 is a diagram illustrating scanning patterns of scanning beamsemitted through the bottom window of FIG. 1E;

FIG. 26 is a diagram illustrating scanning patterns of scanning beamsemitted through the bottom window of the present invention;

FIG. 27 is a diagram comparing the bar code readable area of the barcode reader of the present invention with that of the conventional barcode reader;

FIG. 28 is a diagram illustrating the passages until the beam reflectedby the bar code arrives at the detector in the bar code reader;

FIG. 29 is a diagram illustrating the arrangement of the source of lightin the conventional bar code reader and the optical passages of thescanning beams emitted through the bottom window and the side window;

FIG. 30 is a diagram illustrating the arrangement of the source of lightin the bar code reader of the present invention and the optical passagesof scanning beams emitted through the bottom window and the side window;

FIG. 31 is a diagram illustrating the arrangement of a light-receivingmeans in the bar code reader, bar code readable area and the depth ofthe bar code reader according to the prior art;

FIG. 32 is a diagram illustrating the arrangement of a light-receivingmeans in the bar code reader, bar code readable area and the depth ofthe bar code reader according to the present invention;

FIG. 33A is a front view of a concave mirror used for the bar codereader of the present invention;

FIG. 33B is a side view of the concave mirror used for the bar codereader of the present invention;

FIG. 34 is a perspective view illustrating how to mount the concavemirrors of FIGS. 33A and 33B on the lower frame and how to adjust themounting position;

FIG. 35A is a front view of a bottom mirror used for the bar code readerof the present invention;

FIG. 35B is a side view of the bottom mirror used for the bar codereader of the present invention;

FIG. 36 is a perspective view of when the bar code reader is viewed fromthe bottom side to illustrate the arrangement of adjustment screws foradjusting the mounting angles of the concave mirror and of the bottommirror;

FIG. 37A is a perspective view of the bar code reader of the embodimentof the present invention in which protrusions are formed on the surfaceof the bottom window;

FIG. 37B is a side view of FIG. 37A;

FIG. 38 is a perspective view of a control unit provided inside the barcode reader of the present invention;

FIG. 39 is a diagram illustrating the arrangement of the control unitinside the conventional bar code reader and its problems;

FIG. 40 is a diagram illustrating the arrangement of the control unitinside the bar code reader of the present invention and its effects;

FIG. 41 is a diagram illustrating the arrangement of connectors on theback surface of the bar code reader of the present invention;

FIG. 42 is a perspective view illustrating a state where a cover isremoved from the bottom scanner portion of the bar code reader toillustrate the state of mounting the control unit on the lower frame;

FIG. 43 is a perspective view illustrating a state where the controlunit is removed from the state of FIG. 42;

FIG. 44A is a diagram illustrating the internal constitution of the VLDmodule and the state of laser beam emitted from the VLD module;

FIG. 44B is a diagram of characteristics illustrating the bar codereadable area as a distance from the aperture when the laser beam has anoptimum diameter;

FIG. 45 is a diagram illustrating a difference in the diameter of thebeam emitted from a semiconductor laser depending upon the verticaldirection and the horizontal direction;

FIG. 46A is a diagram illustrating a state where the laser beam in thehorizontal direction is passing through an aperture;

FIG. 46B is a diagram illustrating a state where the laser beam in thevertical direction is passing through an aperture;

FIG. 47 is a diagram illustrating changes in the diameter of the laserbeam depending upon the distance from the aperture using an aperture ofan ordinary diameter, an aperture of a large diameter, and a lens havinga large focal distance;

FIGS. 48A and 48B are diagrams illustrating a problem arising when useis made of a collimator lens having a small f-value, wherein FIG. 48A isa diagram illustrating a change in the diameter of the laser beam in thevertical direction, and FIG. 48B is a diagram illustrating a change inthe laser beam in the horizontal direction;

FIGS. 49A and 49B are diagrams illustrating a problem arising when useis made of a collimator lens having a large f-value, wherein FIG. 49A isa diagram illustrating a change in the diameter of the laser beam in thehorizontal direction, and FIG. 49B is a diagram illustrating a change inthe diameter of the laser beam in the vertical direction;

FIG. 50A is a diagram illustrating a principle for changing the beamdiameter using the rectangular prism;

FIG. 50B is a diagram illustrating a change in the diameter of the laserbeam that has passed through the rectangular prism;

FIG. 51A is a diagram illustrating the diameter of the beam of beforethe beam is incident upon the rectangular prism of FIG. 50B;

FIG. 51B is a diagram illustrating the diameter of the beam emitted fromthe rectangular prism of FIG. 50B;

FIG. 52 is a diagram illustrating the constitution of the VLD moduleusing the rectangular prism and a change in the laser beam;

FIG. 53A is a diagram illustrating a principle for changing the beamdiameter of when the direction of the rectangular prism is changed;

FIG. 53B is a diagram illustrating a change in the diameter of the laserbeam that has passed through the rectangular prism;

FIG. 54A is a diagram illustrating the diameter of the beam of beforethe beam is incident upon the rectangular prism of FIG. 53B;

FIG. 54B is a diagram illustrating the diameter of the beam emitted fromthe rectangular prism of FIG. 53B;

FIG. 55 is a diagram illustrating the constitution of the laser moduleusing the rectangular prism and a change in the diameter of the laserbeam;

FIG. 56A is a diagram illustrating a problem arising when a beamincident upon the rectangular prism is not a parallel beam;

FIG. 56B is a diagram illustrating an example where the collimator lensis turned to solve the problem of FIG. 56A;

FIG. 57 is a diagram illustrating a prism that can be used for a barcode reader of the present invention to substitute for the rectangularprism;

FIGS. 58A to 58C are diagrams illustrating examples for changing thebeam diameter by using means other than the prism, wherein FIG. 58A is adiagram illustrating a combination of a convex cylindrical lens and aconcave cylindrical lens, FIG. 58B is a diagram illustrating acombination of a concave cylindrical lens and a convex cylindrical lens,and FIG. 58C is a diagram illustrating the use of a cylindrical lens ofthe type in which a concave lens and a convex lens are formed as aunitary structure;

FIG. 59 is a diagram illustrating the constitution of an optical systemof the bar code reader for generating two scanning beams by splittingthe laser beam;

FIG. 60A is a diagram illustrating a beam-splitting means;

FIG. 60B is a diagram illustrating another beam-splitting means;

FIG. 61A is a plan view of the VLD module of the present inventionincorporating prism, half-mirror, collimator lens, etc.;

FIG. 61B is a side view of the VLD module of FIG. 61A;

FIG. 62A is a plan view of a block for holding the collimator lens; and

FIG. 62B is a front view of the block for holding the collimator lens.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Described below with reference to the accompanying drawings arepreferred embodiments of the present invention.

FIG. 2A illustrates the appearance of a bar code reading apparatus(hereinafter referred to as a bar code reader) 1 of the presentinvention. The bar code reader 1 shown in FIG. 2A contains a source oflight (such as a semiconductor laser or the like) therein, emitsscanning beams through reading windows to scan the bar code, andreceives the beams reflected by the bar code to read the bar code.

The bar code reader 1 can be roughly divided into two units, i.e., aside scanner portion 2 and a bottom scanner portion 3. The side scannerportion 2 has a reading window called side window 4. The scanning beamfrom the side scanner portion 2 is emitted nearly in a horizontaldirection through the side window 4, and scans the article passing onthe bar code reader 1.

The bottom scanner portion 3 has a reading window called bottom window5. The scanning beam emitted from the bottom window 5 is directedupwards. In order that the article having a bar code is scanned by thescanning beams from different directions, the scanning beam is emittedthrough the bottom window 5 being slightly tilted toward the side window4 to thereby scan the article passing on the bar code reader 1. The sidescanner portion 2 and the bottom scanner portion 3 constituting the barcode reader 1 have their respective optical systems therein forgenerating scanning beams. Constitutions of these optical systems willbe described later in detail.

In FIG. 2A, reference numeral 6 denotes a dip switch which is used forsetting a variety of operations of the bar code reader 1. Referencenumeral 7 denotes a restart switch which is used for resetting theoperation of the bar code reader 1. Though not shown in FIG. 2A, the barcode reader 1 is provided with an indicator such as LED for informingthe operator of the fact that the bar code cannot be read, a speaker forproducing alarm sound, etc.

Furthermore, the surface of the bar code reader 1 having the bottomwindow 5 works as a scale which, when an article is placed thereon,measures the weight of the article. When the price of the articlecorresponds to the weight of the article, the prices of the individualarticles can be calculated by measuring the weights of the articles.

FIG. 2B illustrates a state where the bar code reader 1 of FIG. 2A isinstalled on an accounting counter (check-out counter) in a store. Thebar code reader 1 is installed on the accounting counter 11 such thatthe counter surface 12 of the accounting counter 11 is flush with theupper surface 13 of the bar code reader 1 which is provided with thebottom window 5. Therefore, the lower portion of the bar code reader 1is buried in the accounting counter 11.

The operator stands at a position facing the side scanner portion 2 ofthe accounting counter 11, passes an article, to which a bar code isattached, over the bar code reader 1, so that the article is irradiatedwith the scanning beam thereby to read the bar code attached to thearticle.

Since the counter surface 12 is flush with the upper surface 13 of thebar code reader 1 having the bottom window 5, the operator passes thearticle on the bar code reader 1 in a manner to come into contact withthe counter surface 12 to thereby read the bar code.

FIG. 3 illustrates the arrangement of an optical system in the bar codereader 1 and the passages of beams emitted from a laser beam source. AVLD (visible laser diode) module 21 is used as the source of laser beam.The VLD module 21 contains a semiconductor laser, and a laser beamgenerated by the semiconductor laser is emitted as a scanning beam. TheVLD module 21 is installed at a position remotest from the side scannerportion 2 and emits a laser beam toward the side scanner portion 2.

The bar code reader 1 has only one VLD module 21 as a source of light,but has two reading windows, i.e., side window 4 and bottom window 5.Therefore, the laser beam emitted from the VLD module 21 is split on itsway into two by a half-mirror 22 which is a splitter. The half-mirror 22reflects part of the laser beam emitted from the VLD module 21, andtransmits part of the laser beam, to thereby split the laser beam intotwo. A scanning beam to be emitted through the side window 4 is obtainedfrom one of the split beams, and a scanning beam to be emitted throughthe bottom window 5 is obtained from the other one of the split beams.

Reference numerals 23 and 24 denote reflection mirrors which reflectlaser beams reflected by the half-mirror 22 so that they are incidentupon a polygon mirror 25. The reflection mirrors 23 and 24 are of asmall square shape. A concave mirror 30 is provided neighboring thehalf-mirror 22. A through hole 31 is formed in the center of the concavemirror 30, and the laser beam emitted from the VLD module 21 is incidentupon a polygon mirror 25 passing through the hole 31.

The polygon mirror 25 is a polyhedron having a plurality of reflectionplanes and having, in this case, four reflection planes. The polygonmirror 25 is mounted on a polygon motor 20 and is rotated by the polygonmotor 20. Onto the reflection planes of the polygon mirror 25 areincident, from different directions, a laser beam that has passedthrough the hole 31 of the concave mirror 30 after having passed throughthe half-mirror 22 and a laser beam reflected by the reflection mirrors23 and 24 after reflected by the half-mirror 22. Since the polygonmirror 25 is rotated as described above, the laser beams reflected bythe reflection planes of the polygon mirror 25 are converted intoscanning beams that describe arcs.

The reflection planes of the polygon mirror 25 are tilted atpredetermined angles, and the laser beams are reflected by thereflection planes in predetermined angular directions. The reflectionplanes are tilted at different angles. The angles of reflection planesof the polygon mirror 25 need not be different for all reflectionplanes.

Reference numeral 26 denotes a first mirror system for emitting the beamreflected by the polygon mirror 25 through the bottom window 5, andreference numeral 27 denotes a second mirror system for emitting thebeam reflected by the polygon mirror 25 through the side window 4. Themirror systems 26 and 27 are each constituted by a combination of aplurality of mirrors. The mirror systems 26 and 27 work to divide ascanning beam formed by the polygon mirror 25 into a plurality ofscanning lines in order to increase the number of scanning lines emittedthrough the side window 4 and the bottom window 5. Moreover, thedirections and inclinations of the reflection planes of mirrorsconstituting the mirror systems 26 and 27 are so set that the scanninglines emitted through the side window 4 and the bottom window 5 willhave a variety of scanning directions (angles).

On the first mirror system 26 is incident a scanning beam that haspassed through the half-mirror 2 and is reflected by the reflectionplane of the polygon mirror 25. This scanning beam is so reflected aswill be emitted nearly upwardly through the bottom window 5. On thesecond mirror system 27 is incident a scanning beam that is reflected bythe reflection plane of the polygon mirror 25 after having beenreflected by the half-mirror 22 and the reflection mirrors 23, 24. Thisscanning beam is so reflected as will be emitted nearly in a horizontaldirection through the side window 4.

The scanning beams emitted from the side window 4 and the bottom window5 are projected onto the article passing on the bar code reader 1 tothereby scan the bar code surfaces. The scanning beams having scannedthe bar code surfaces are reflected by the bar code surfaces, and areincident upon the bar code reader 1 through the side window 4 and thebottom window 5. The beams reflected by the bar code and are incidentthrough the side window 4 and the bottom window 5 arrive at the polygonmirror 25 travelling through the same passages through which thescanning beams were emitted, and are reflected by the reflection planesof the polygon mirror 25.

Described below are the passages of incidence of the reflected beam fromthe bar code to the bar code reader 1. In FIG. 3, reference numeral 28denotes a first detector which detects a beam reflected by the bar codeand is incident upon the bar code reader 1 through the bottom window 5.The light-receiving surface of the first detector 28 is faced to adirection opposite to the side scanner portion 2. Reference numeral 29denotes a second detector which detects a beam reflected by the bar codeand is incident upon the bar code reader 1 through the side window 4.The light-receiving surface of the second detector 29 is tilteddownward. The beams reflected by the bar code and received by the firstand second detectors 28 and 29 are electrically processed, convertedinto binary signals, decoded by a decoding circuit that is not shown,and are output to an external unit (e.g., POS terminal).

The beam reflected by the bar code and incident onto the bottom window 5is reflected by the reflection plane of the polygon mirror 25, falls onthe concave mirror 30, and is focused on the light-receiving surface ofthe first detector 28 by the concave mirror 30. The beam reflected bythe bar code surface of the article has been scattered and, hence, thereflected beam incident on the bar code reader 1 has been broadened tosome extent. In this state, a decreased amount of the reflected beamarrives at the light-receiving surface of the first detector 28, and thebeam is not obtained in an amount sufficient for reading the bar code.Therefore, the bar code reader 1 of FIG. 3 focuses the reflected beamusing the concave mirror 30 to increase the amount of the reflected beamreceived by the first detector 28.

The concave mirror 30 works to fold the reflected beam back, i.e.,reflects the beam from the bar code through the polygon mirror 25 towardthe first detector 28. Therefore, a long optical passage is realized inthe device though its full length is small. The through hole 31 formedin the center of the concave mirror 30 permits the laser beam emittedfrom the VLD module 21 and incident upon the polygon mirror 25 to passthrough.

As described above, the beam reflected by the bar code is incident onthe detector travelling through the same passages as those through whichthe scanning beam was emitted. In order that the bar code can be mostefficiently read out, the optical axis of the beam emitted from the VLDmodule 21 must be in agreement with the optical axis of the reflectedbeam incident on the first detector 28. Therefore, the concave mirror 30must be arranged on the optical axis of the laser beam emitted from theVLD module 21 but must not intercept the optical axis of the emittedbeam. For this purpose, the concave mirror 30 of FIG. 3 is provided atthe central portion thereof with a hole 31 through which the beamemitted from the VLD module 21 is permitted to pass.

Reference numeral 32 denotes a Fresnel lens which focuses the beamreflected by the bar code and is incident through the side window 4.This action is the same as that of the above-mentioned concave mirror30. A small reflection mirror 24 is disposed in front of the Fresnellens 32. The optical axis of the beam reflected by the reflection mirror24 is also in agreement with the optical axis of the beam that isreflected by the bar code and is incident on the Fresnel lens 32. Asdescribed above, however, the beam reflected by the bar code isbroadened and only part of the beam incident on the Fresnel lens 32 isintercepted by the reflection mirror 24; i.e., most of the beamreflected by the bar code is incident upon the Fresnel lens 32.

The Fresnel lens 32 is tilted to meet the angle of incidence of the beamreflected by the polygon mirror 25. The reflected beam focused by theFresnel lens 32 is upwardly reflected by a bottom mirror 33 provided onthe bottom surface of the bar code reader, and arrives at thelight-receiving surface of the second detector 29 which faces downward.

Here, the bottom scanner portion 3 is constituted by the first mirrorsystem 26, concave mirror 30 and first detector 28, and the side scannerportion 2 is constituted by reflection mirrors 23, 24, second mirrorsystem 27, Fresnel lens 32, bottom surface mirror 33 and second detector29. The VLD module 21, half-mirror 22 and polygon mirror 25 are sharedby the bottom scanner portion 3 and the side scanner portion 2.

The thus constituted bar code reader 1 further has a printed board 34arranged on the bottom surface thereof. On the printed board 34 aremounted a circuit for controlling the turn-on of the laser, a circuitfor controlling the operation of the detector, a circuit for controllingthe rotation of the polygon motor, and a decoder circuit for decodingthe bar code based upon the reflected beam detected by the detector. Theprinted board 34 has a connector 37 for connection to the external unit.An interface (I/F) cable 35 is connected to the connector 37, and thedecoded bar code data are output.

FIG. 4 is a diagram illustrating a state where a bar code 8 is scannedby a scanning beam emitted from the bar code reader 1. As shown in FIG.4, a scanning beam LH is emitted nearly in a horizontal direction (ortilted slightly upwards) through the side window 4. Through the bottomwindow 5, on the other hand, a scanning beam LV is emitted upwards. Thebeam emitted through the bottom window 5 is slightly tilted toward theside window 4. Therefore, the scanning beams emitted through both theside window 4 and the bottom window 5 are focused at a portion A of FIG.4. With an article with bar code being passed through this position,therefore, the article is scanned simultaneously (or at different times)with the scanning beams LH and LV emitted from different directionsthrough the side window 4 and the bottom window 5.

Therefore, even when the bar code 8 is not faced to the side window 4 orto the bottom window 5, it becomes more probable that the bar code 8 isirradiated with the scanning beam emitted through either the side window4 or the bottom window 5, and the probability for reading the bar code 8becomes high.

The scanning beam for scanning the bar code 8 is reflected by thesurface of the article 9 to which the bar code 8 is attached. Here,however, the reflected beam RF is scattered as shown in FIG. 4.Therefore, even when the bar code 8 is located nearly perpendicularly tothe bar code reader 1 and is faced to the direction opposite to the sidewindow 4 as represented by a position B, part RFp of the beam reflectedby the bar code 8 arrives at the bottom window 5. In particular, thescanning beam emitted through the bottom window 5 is upwardly directed.When the bar code 8 in a state as represented by the position B isscanned, therefore, it becomes more probable that the beam reflectedfrom the bar code 8 is incident upon the bottom window 5.

As described above, the bar code 8 of the article 9 passing the bar codereader 1 is scanned by the scanning beams from different directions.Therefore, the bar code 8 can be read out unless the bar code 8 islocated at a position C where it faces neither the side window 4 nor thebottom window 5, and is not irradiated by the scanning beam.

FIG. 5 illustrates an outer size of the bar code reader 1 of FIG. 2A.The bar code reader 1 has a width W of about 292 mm and a height H ofabout 247 mm. Moreover, the bar code reader 1 has a depth D of about 508(or 430 mm), and a height H1 of about 120 mm from the bottom surface tothe counter surface 12. The bar code reader 1 may have a depth D thatmeets the width of the accounting counter on which the bar code reader 1is installed.

FIG. 6 is a diagram illustrating the optical system in the bar codereader 1. In FIG. 6, arrows represent passages of laser beams, and thedirections of arrows represent the directions in which the laser beamsare emitted. In FIG. 6, the internal constitution of the bar code reader1 is drawn as divided into the side scanner portion 2 and the bottomscanner portion 3. In practice, the VLD module 21 is shared but is drawnbeing divided in FIG. 6 for the sake of convenience. The VLD module 21in the side scanner portion 2 will include the half-mirror.

In the bottom scanner portion 3, the laser beam emitted from the VLDmodule 21 falls on the polygon mirror 25, and is reflected by thereflection plane of the polygon mirror 25. Thereafter, the laser beam isreflected by the first mirror system 26 and is projected to the bar code8 through the bottom window 5. The bottom window 5 is constituted by twopieces of glass plate and prevents water or the like from entering intothe bar code reader 1.

The glass plate is composed of a sapphire glass or the like glass havinga high hardness. If the glass surfaces are scratched and fouled beingcontacted by the articles, the laser beam may pass through in decreasedamounts. Of the two glass plates constituting the bottom window 5,therefore, the lower glass plate which is less likely to be contacted bythe articles is secured to the device, and the upper glass plate whichis very likely to be contacted by the articles is allowed to be renewedas required. Therefore, the upper glass plate that is scratched can berenewed, and a drop in the performance for reading bar codes, that stemsfrom the reduction in the amount of the laser beam passing through thebottom window 5, is avoided. The lower glass plate which is littlelikely to be contacted by the articles is less likely to be scratched onits surfaces than the upper glass plate. Therefore, the lower glassplate need not be composed of a hard and expensive glass such assapphire glass.

Though the details will be described later, scanning patterns areemitted in a total of ten directions from the bottom scanner portion 3,the scanning pattern in each direction consisting of four scanninglines. The scanning patterns are emitted in ten directions after everyrevolution of the polygon mirror 25, and the bar code is scanned by atotal of 40 scanning lines. The four scanning lines constituting eachscanning pattern corresponded to each reflection plane of the polygonmirror 25.

The beam reflected by the bar code 8 is incident on the first mirrorsystem through the bottom window 5 and is reflected toward the polygonmirror 25. Thereafter, the beam reflected by the bar code 8 is reflectedby the reflection plane of the polygon mirror 25 and is focused andreflected by the concave mirror 30 toward the first detector 28. Apin-photodiode can be used as the first detector 28.

In the side scanner portion 2, on the other hand, the laser beam emittedfrom the VLD module 21 and reflected by the half-mirror is reflected bya plurality of reflection mirrors 23, and is guided to the polygonmirror 25. The scanning beam reflected by the reflection plane of thepolygon mirror 25 is reflected by the second mirror system 27, and isemitted through the side window 4 to scan the bar code 8. Like thebottom window 5, the side window 4 is constituted by two pieces ofwindow glasses. In reading the bar code 8, the article 9 is less likelyto come into contact with the side window 4. Therefore, the glass plateused for the side window 4 may be an ordinary glass instead of a hardglass.

Scanning patterns are emitted in six directions through the side window4, the scanning pattern in each direction consisting of four scanninglines; i.e., a total of 24 scanning lines are emitted. This will bedescribed later in detail.

The beam reflected by the bar code 8 is incident on the bar code reader1 through the side window 4, reflected by the second mirror system 27and by the reflection plane of the polygon mirror 25, and is focused bythe Fresnel lens 32. The beam is then reflected by the bottom mirror 33and is received by the second detector 29. A pin-photodiode can be usedas the second detector 29. The constitution of a combination of theFresnel lens 32 and the bottom mirror 33 may be substituted by a concavemirror having a function for focusing light.

A disturbance light sensor 36 shown in FIG. 6 detects a change in theamount of light around the bar code reader 1, controls the operation ofthe bar code reader 1 based upon the result thereof, and controls theturn-on of the VLD module 21.

Arrangement of the optical system in the bar code reader 1 will bedescribed in further detail.

FIG. 7 illustrates a state where an upper cover and a lower cover areremoved from the bottom scanner portion 3 of the bar code reader 1.Reference numeral 5B denotes the lower glass plate of the two glassplates constituting the bottom window 5. In FIG. 7, reference numeral 41denotes a lower frame, 41F denotes a flange portion of the lower frame41, reference numeral 42 denotes an upper frame, 42F denotes a flangeportion of the upper frame 42, and reference numeral 43 denotes a coverportion of the side scanner portion 2. The lower frame 41 and the upperframe 42 are divided up and down at the positions of flange portions 41Fand 42F. Mirrors constituting the bottom scanner portion 3 are mountedon the inner wall surfaces of the lower frame 41 and of the upper frame42.

FIGS. 8A and 8B are a plan view and a side view of the bar code reader 1shown in FIG. 7. The cover portion 43 in which the side window 4 isprovided can be divided from the lower frame 41 of the bar codereader 1. Inside the cover portion 43 is provided a mirror frame 44 towhich is stuck a mirror that constitutes a portion of the second mirrorsystem 27.

FIG. 9 illustrates a state where the lower frame 41 only is removed fromthe bar code reader 1 shown in FIG. 7. The polygon mirror is disposednearly at the central portion of the lower frame 41. FIG. 9 shows aplate 51 for installing the polygon mirror but does not show the polygonmirror. A gap 52 is formed under the plate 51 to permit the passage of alaser beam from the reflection mirror 23 to the reflection mirror 24. Onthe lower frame 41 are mounted a total of nine mirrors for constitutingthe first mirror system 26 or the second mirror system 27. Among them,ZB2, VBRR, VBLL, HBR2, HBL2, ZML2 and ZMR2 are mirrors constituting thefirst mirror system 26. Mirrors VSR1 and VSL1 constitute a portion ofthe second mirror system 27.

The mirrors ZMR2 and ZML2 are mounted on the side surface of the lowerframe 41 and extend along the lengthwise direction of the lower frame41. The mirror ZB2 is so disposed that its reflection plane is upwardlydirected. The angle of the reflection plane of the mirror ZB2 can besuitably adjusted. The mirrors VBRR and VBLL are arranged on thesurfaces of the lower frame 41 most remote from the side scannerportion, with their reflection planes being tilted slightly upwardly soas to face the polygon mirror.

The mirrors VSR1 and VSL1 are mounted on the side surfaces of the lowerframe 41 with their reflection planes being slightly tilted upward.

Reference numeral 53 denotes a printed board, and a second detector 29is mounted on a portion thereof. The printed board 53 is mounted on thelower frame 41 such that the light-receiving surface of the seconddetector 29 is downwardly tilted. This arrangement makes it possible toreduce the depth of the device.

The Fresnel lens 32 is mounted in a tilted manner between the printedboard 53 and the polygon mirror. Furthermore, the reflection mirror 24is provided in front of the Fresnel lens 32 and on the optical axisthereof.

The VLD module is held under the lower surface of the mirror ZB2, and alaser beam is emitted from this position. The reflection mirror 23 ismounted at the back of the mirror ZB2 to reflect the laser beam passingthrough a gap between the mirror ZB2 and the lower frame 41 toward thereflection mirror 24.

The first detector 28 is provided on the lower surface of the device.The light-receiving surface of the first detector 28 faces the side ofthe reflection mirror 23, and an opening 54 is formed on the front sideof the light-receiving surface of the first detector 28 to guide thelaser beam reflected by the concave mirror 30 toward the first detector28. The opening 54 has a V-shape to meet an optical passage in which thereflected beam is focused by the concave mirror 30. The first detector28 is mounted on a printed board 55.

FIG. 10A illustrates the lower frame 41 that is viewed from the upperside, and FIG. 11 is a side sectional view of the lower frame 41.

As shown in FIG. 10A or 11, the polygon mirror 25 has an axis ofrotation 25, and is provided nearly at the center of the lower frame 41but closer to the side scanner portion. At the back of the Fresnel lens32 is provided the bottom mirror 33 with its reflection plane beingupwardly faced. The first detector 28 is mounted on the bottom surfaceof the lower frame 41. The first detector 28 is mounted on the printedboard 55. The opening 54 of nearly a V-shape is formed on the side ofthe light-receiving surface of the first detector 28, and the beamreflected by the concave mirror 30 is incident on the first detector 28through the opening 54.

The VLD module 21, reflection mirrors 23, 24, Fresnel lens 32, polygonmirror 25, first detector 28, second detector 29 and concave mirror 30are arranged in the lower frame 41 along the center line CL (that is, ina specified plane defined by the centerline CL in FIG. 10A) in such amanner that the optical axes of the rays of light are in agreement. TheVLD module 21 and concave mirror 30 are arranged under the mirror ZB2.In FIG. 10A, the mirror ZB2 has been partly cut away so that thearrangement of the VLD module 21 can be seen.

Referring to FIG. 11, the first detector 28 is disposed on the bottomsurface of the lower frame 41 and does not intercept the passage of beamemitted from the VLD module 21 or of the beam reflected by the bar code.The mirror ZB2 is mounted being slightly tilted. The reflection mirrors23 and 24 are attached to the ends of slender frames and will not tointercept the passages of the beams.

Protrusions 56 are formed on the bottom surfaces and on the sidesurfaces of the mirrors to define the positions and angles of themirrors. The mirrors mounted on the lower frame are secured by beingabutted to the protrusions 56. Thus, the mirrors are mounted on thelower frame 41 facing predetermined directions at predetermined angles.

In the embodiment shown in FIG. 10A, the first detector 28 is arrangedin the lower frame 41 along the center line CL. As shown in FIG. 10B,however, the first detector 28 may be disposed in the lower frame 41 ata position deviated from the center line CL. In this case, the concavemirror 30 must be so arranged that it is tilted at a directionperpendicular to the center line CL of the lower frame 41, so that thebeam reflected by the concave mirror 30 is focused to the first detector28.

The constitution of the lower frame 41 shown in FIG. 10B is quite thesame as the constitution of the lower frame 41 described with referenceto FIG. 10A except the position of the first detector 28 and thedirection of the concave mirror 30, and the same constituent members aredenoted by the same reference numerals but their description is notrepeated.

FIG. 12 illustrates the lower frame 41 of the device and the upper frame42 placed thereon. The mirrors are stuck to the inside of the upperframe 42. The upper frame 42 is provided with a total of ten mirrorsZBRl, ZBL1, HBR1, HBL1, VBR1, VBL1, VBR2, VBL2, ZMR1, ZML1. Thesemirrors constitute a portion of the first mirror system 26. Thesemirrors are disposed with their reflection planes being faced slightlydownwardly and being faced to the mirrors that are mounted on the lowerframe 41 to constitute the bottom scanner portion.

FIGS. 13A to 13D illustrate the mirror frame 44 mounted inside the coverportion 43 of the side scanner portion 2 as viewed from the upperdirection, front direction, bottom direction and side direction. On theinside of the mirror frame 44 are mounted a total of eight mirrors ZHR,ZHL, ZRR, ZLL, VSR2, VSL2, ZR, ZL. These eight mirrors constitute aportion of the second mirror system 27. In the side view of FIG. 13D,the left side corresponds to the side where the operator stands or tothe side of the side window. Among the eight mirrors, the reflectionplanes of the mirrors ZR and ZL are tilted upward, and the reflectionplanes of the remaining six mirrors are tilted slightly downward. Thereflection planes of the six mirrors other than the mirrors ZR and ZLare so disposed as to be directed toward predetermined positions on theoutside of the side scanner portion 2.

FIG. 14 is a diagram illustrating the shapes of the upper six mirrorsVSL2, ZLL, ZHL, ZHR, ZRR, VSR2 among the mirrors mounted on the mirrorframe 44 and their rough positions of mounting. These six mirrors aremounted on the mounting surfaces on the inside of the mirror frame 44using an adhesive or the like.

FIG. 15 is a side sectional view of the bar code reader 1 in a statewhere the lower frame 41, upper frame 42, cover portion 43 and mirrorframe 44 are assembled. The mirrors mounted on the upper frame 42 havereflection planes that are faced slightly downwardly, and the beamsreflected by the mirrors mounted on the upper frame 42 are incident onthe mirrors mounted on the lower frame 41. The height of the positionsof the reflection planes of the mirrors ZR, ZL mounted on the mirrorframe 44 is nearly the same as the height of the positions of thereflection planes of the mirrors VSR1, VSL1 mounted on the lower frame41.

In FIG. 15, the second detector 29 is so disposed that thelight-receiving surface thereof is downwardly faced, and the printedboard 53 is disposed to be nearly perpendicular to the bar code reader 1to meet therewith. This arrangement makes it possible to decrease thedepth of the bar code reader 1 compared with that of when the printedboard 53 is horizontally arranged. Furthermore, the Fresnel lens 32 andthe bottom mirror 33 that guide the beam reflected by the bar code tothe second detector 29 are provided at positions where they will notintercept the passages of scanning beams that are reflected by thepolygon mirror 25 toward the mirrors VSL1, ZL, etc.

FIG. 16 is a diagram schematically illustrating the passages of thescanning beams emitted from the bottom scanner portion 3 through thebottom window 5, and FIG. 17 is a diagram schematically illustrating thepassages of the scanning beams emitted from the side scanner portion 2through the side window 4.

In the case of the bottom scanner portion 3 shown in FIG. 16, the laserbeam emitted from the VLD module 21 and reflected by the reflectionplane of the polygon mirror 25 is scanned by the mirrors ZBR1, ZBL1,HBR1, HBL1, VBR1, VBL1, VBR2, VBL2, ZMR1, ZML1 mounted on the upperframe 42. When the polygon mirror 25 rotates in the clockwise direction,the scanning is effected in the order of mirrors ZMR1, VBR2, VBR1, HBR1,ZBR1, ZBL1, HBL1, VBL1, VBL2 and ZML1.

Next, the beam reflected by the mirrors on the inside of the upper frame42 is projected onto the mirrors mounted in the lower frame 41.

The scanning beam reflected by the mirror ZMR1 is upwardly reflected bythe mirror ZMR2 and is emitted as a scanning pattern ZMR through thebottom window 5. The scanning beams reflected by the mirrors VBR2 andVBR1 are upwardly reflected by the mirror VBRR and are emitted asscanning patterns VBR2, VBR1 through the bottom window 5. The scanningbeam incident on the mirror VBRR due to the mirror VBR2 and the scanningbeam incident on the mirror VBRR due to the mirror VBR1 have differentpositions of incidence and different angles, and are emitted through thebottom window 5 as scanning beams having different directions andangles.

The scanning beam reflected by the mirror HBR1 is upwardly reflected bythe mirror HBR2 and is emitted as a scanning pattern HBR through thebottom window 5. The scanning beam reflected by the mirror ZBR1 isupwardly reflected by the mirror ZB2 and is emitted as a scanningpattern ZBR through the bottom window 5. The same holds even in the caseof the mirrors ZBL1, HBL1, VBL1, VBL2 and ZML1. The scanning beamreflected by the mirror ZBL1 is upwardly reflected by the mirror ZB2 andis emitted as a scanning pattern ZBL. The scanning beam reflected by themirror HBL1 is upwardly reflected by the mirror HBL2 and is emitted as ascanning pattern HBL. The scanning beams reflected by the mirrors VBL1and VBL2 are upwardly reflected by the mirror VBLL to form scanningpatterns VBL1 and VBL2. Then, the scanning beam reflected by the mirrorZML1 is upwardly reflected by the mirror ZML2 and is emitted as ascanning pattern ZML thereby to end a scanning cycle.

Here, as shown in FIG. 12, the scanning beam reflected by the mirrorZML1 reaches the mirror ZML2 traversing the inside of the bottom scannerportion 3. Thus, since the scanning beam partly traverses the inside ofthe bottom scanner portion 3, obstacles must be removed from the insideof the bottom scanner 3 to form space that will not intercept thescanning beams.

In the bar code reader 1 of this embodiment, therefore, the VLD module21, concave mirror 30 and the like are placed at the ends of the deviceas shown in FIG. 15, and the first detector 28 is mounted on the bottomsurface of the device. Furthermore, the polygon mirror 25 is mounted ona position where it will not intercept space inside the bottom scannerportion 3.

The mirrors constituting the bottom scanner portion 3 are mounted on thewall surfaces on the inside of the lower frame 41 and the upper frame 42that are split into up and down. Therefore, there is no need to providea structure for arranging the mirrors in space inside the bottom scannerportion 3. With the mirrors being arranged as described above, spaceinside the bottom scanner portion 3 can be effectively utilized.

In the side scanner portion 2 shown in FIG. 17, on the other hand, thescanning beam emitted from the VLD module 21 and reflected by thereflection mirrors 23, 24 and by the polygon mirror 25, first, falls onthe mirrors VSR1 and VSL1 mounted on the lower frame 41 and on themirrors ZR and ZL mounted on the mirror frame 44. The scanning iseffected in the order of mirrors VSL1, ZL, ZR, VSR1.

The scanning beam reflected by these mirrors is then reflected by sixmirrors of the upper side mounted on the mirror frame 44. First, thescanning beam reflected by the mirror VSL1 is reflected nearly in thehorizontal direction by the mirror VSL2 and is emitted as a scanningpattern VSL through the side window 4. The scanning beam reflected bythe mirror ZL falls on the mirror ZLL and is emitted as a scanningpattern ZLL through the side window 4. Then, the scanning beam reflectedby the mirror ZL is reflected by the mirror ZHL, and is emitted as ascanning pattern ZHL through the side window 4.

Next, the scanning beam reflected by the mirror ZR is first reflected bythe mirror ZHR and is emitted as a scanning pattern ZHR through the sidewindow 4. Next, the scanning beam reflected by the mirror ZR isreflected by the mirror ZRR, and is emitted as a scanning pattern ZRRthrough the side window 4. Finally, the scanning beam reflected by themirror VSR1 is reflected by the mirror VSR2, and is emitted as ascanning pattern VSR through the side window 4. Thus, a scanning cycleends.

FIG. 18 is a diagram illustrating loci of scanning patterns in tendirections shown in FIG. 16 on the bottom window 5. There are shown lociof scanning patterns reflected by one plane of the polygon mirror 25.FIG. 19 is a diagram illustrating all the scanning patterns reflected byall planes of the polygon mirror 25 and emitted through the bottomwindow 5. As described already, a total of 40 scanning lines are emittedthrough the bottom window 5. The forty scanning lines are grouped intoten groups each consisting of four scanning lines.

Two scanning patterns ZMR and ZML shown in FIG. 18 are nearlyperpendicular to the operator and extend over nearly the whole region ofthe bottom window 5 in the lengthwise direction. Therefore, the articleof which the bar code is to be read out is scanned by at least thescanning patterns ZMR and ZML irrespective of where it may pass on thebottom window 5.

The remaining eight scanning patterns describe loci that are slightlytilted upwardly to intersect the scanning patterns ZMR and ZML. Byemitting the scanning patterns shown in FIGS. 18 and 19, the scanninglines that constitute any scanning pattern scan the bar codeirrespective of whether the bar code may pass on the bar code reader 1at dissimilar angles, contributing to enhancing the ability for readingthe bar code.

Here, symbols attached to the scanning patterns correspond to the mirrornames constituting the first mirror system 26 as described withreference to FIG. 16, and these scanning patterns are reflected by themirrors having the corresponding names.

Moreover, the reflection planes of the polygon mirror have differentangles. Therefore, the scanning patterns emitted through the bottomwindow 5 and corresponding to such reflection planes have four scanninglines which are nearly in parallel and scan the positions separated by apredetermined distance depending upon the angles of the reflectionplanes of the polygon mirror. Thus, a scanning pattern is constituted bya plurality of scanning lines that are separated by a predetermineddistance. Therefore, the probability of scanning the bar code by thescanning lines is enhanced, contributing to further enhance the abilityfor reading the bar code.

FIG. 20 is a diagram illustrating scanning patterns emitted through theside window 4. Through the side window 4 are emitted six scanningpatterns VSR, VSL, ZRR, ZLL, ZHR, ZHL each consisting of four scanninglines that are nearly in parallel and are spaced apart by apredetermined distance. The names of these scanning patterns correspondto the names of the mirrors constituting the side scanner portion 2 asdescribed with reference to FIG. 17, and represent scanning patternsreflected by the mirrors having the same names as in the case of FIG.18. The four scanning lines in a scanning pattern are defined for theirscanning positions depending upon the angle of the reflection plane ofthe polygon mirror 25 as in the case of the scanning pattern emittedthrough the bottom window 5.

The scanning patterns of FIG. 20 are the patterns emitted through theside window 4. As described above, six mirrors other than the mirrorsZR, ZL mounted on the mirror frame 44 are so arranged that theirreflection planes are directed to predetermined positions on the outsideof the side scanner portion 2. Therefore, the scanning patterns approacheach other as they separate from the side window 4. The six scanningpatterns approach most at a position which is most suited for readingthe bar code, and it becomes most probable at this position that the barcode passing on the bar code reader is scanned by the side patterns.

The scanning patterns emitted through the bottom window 5 as well as thescanning patterns emitted through the side window 4, are symmetricallyarranged on the right and left sides with respect to the center lines.Since every bottom pattern and every side pattern have directions andangles that are different by small amounts, it becomes very probablethat the bar code is traversed by at least one of the scanning lines.

FIGS. 21A to 21D illustrate scanning patterns of either side only amongthe scanning patterns (bottom patterns) emitted through the bottomwindow 5 and the scanning patterns (side patterns) emitted through theside window 4. As described above, the right and left scanning patternsemitted through the side window 4 and the bottom window 5 aresymmetrical relative to the center lines. The scanning patterns of theother side are just the same as the scanning patterns shown in FIGS. 21Ato 21D turned around.

FIG. 21A illustrates scanning patterns VBL1 and VBL2 among the bottompatterns. The scanning pattern VBL1 describes scanning loci that riseslightly toward the right at positions close to the side window 4. Thescanning pattern VBL2 describe scanning loci that rise slightly towardthe right like the scanning pattern VSL1 but at a position closer to theoperator than that of the scanning pattern VBL1. FIG. 21B illustratesthe scanning pattern ZML describing loci which traverse the bottomwindow 5 nearly in the lengthwise direction thereof. Therefore,irrespective of where the article may pass on the bottom window 5, thearticle is scanned by at least the scanning pattern ZML.

FIGS. 21C illustrates scanning patterns HBL and ZBL. The scanningpattern HBL describes scanning loci slightly rising toward the left atpositions close to the side scanner on the left side of the bottomwindow 5. The scanning pattern ZBL, on the other hand, describesscanning loci slightly rising toward the left at positions close to theoperator on the right side of the bottom window 5.

FIG. 21D illustrates left side patterns among the scanning patternsemitted through the side window 4. The scanning pattern VSL extend inthe vertical direction of the side window 4 and describes scanning locithat slightly rise toward the left. The scanning pattern ZLL describesscanning loci that rise toward the right. The scanning pattern ZHLdescribes scanning loci that slightly rise toward the right on the upperside nearly at the center of the side window 4.

Upon generating the above-mentioned scanning patterns, the articlepassing on the bar code reader is irradiated with a total of 64 scanninglines from two directions after every turn of the polygon mirror 25. Asthe article is scanned by an increased number of scanning lines fromdifferent directions and at different angles, it becomes more probablethat the bar code surface is scanned by the scanning line, and readingthe bar code becomes correspondingly more successful.

FIG. 22 is a diagram illustrating the loci of a laser beam emitted fromthe VLD module 21 in the bar code reader 1. The VLD module 21 has theprism 61 for changing the out-going angle of the laser beam and forchanging the diameter of the beam, and the half-mirror 22 for splittingthe laser beam into two.

The laser beam that has passed through the prism 61 and the half-mirror22 is emitted slightly upwardly, passes through the hole 31 formed inthe center of the concave mirror 30, and falls on the polygon mirror 25.The laser beam in the bottom scanner portion 3 reflected by the polygonmirror 25 is incident on the mirror ZBL1 mounted on the upper frame 42and is reflected so as to be once folded back downwardly by the mirrorZBL1, and falls on the mirror ZB2 mounted on the lower frame 41. Themirror ZB2 reflects the scanning beam that is incident thereon toward anupwardly tilted direction. Therefore, a scanning beam forming thescanning pattern ZBL is emitted through the bottom window 5.

On the other hand, the laser beam that has passed through the prism 61and is reflected by the half-mirror 22 falls on the reflection mirror 23passing through space under the mirror ZB2, reflected by the reflectionmirror 23, and falls on the reflection mirror 24 passing through a gap52 under the plate 51 on which the polygon mirror 25 is installed. Thelaser beam reflected by the reflection mirror 23 toward the reflectionmirror 24 is emitted nearly in a horizontal direction.

The reflection mirror 24 reflects the laser beam that is incidentthereon toward an upwardly tilted direction so that it will fall on thepolygon mirror 25. The laser beam incident on the polygon mirror 25 isreflected, and is further upwardly reflected by the mirror VSL1 mountedon the lower frame 41 or by the mirror ZL mounted on the mirror frame44, and is emitted through the side window 4 nearly in the horizontaldirection due to other six mirrors mounted on the mirror frame 44.

In the case of FIG. 22, for example, the scanning beam reflected by thepolygon mirror 25 is incident on the mirror ZL and is reflected upwardly(nearly in a vertical direction). Thereafter, the scanning beam falls onthe mirror ZHL mounted on the mirror frame 44 and is reflected in thehorizontal direction so as to form the scanning pattern ZHL.

FIG. 23 is a perspective view of the lower frame 41 of the bar codereader 1 and illustrates a passage of the laser beam emitted from theVLD module 21 up to the polygon mirror 25. In FIG. 23, the polygonmirror is not diagrammed so that the loci of the ray of beam can beeasily understood, and only the plate 51 is diagrammed on which thepolygon mirror will be installed. The concave mirror is provided underthe mirror ZB2 and is not shown here.

Referring to FIG. 23, the laser beam reflected by the reflection mirror23 is incident on the reflection mirror 24 passing through the gap 52under the plate 51, and is reflected by the reflection mirror 24 towardthe polygon mirror which is in an upwardly tilted direction. On theother hand, the laser beam emitted through the hole in the concavemirror falls directly on the polygon mirror.

FIGS. 24 to 26 illustrate in comparison the scanning patterns emittedfrom the bar code reader of the present invention and from theconventional bar code readers through their bottom windows. FIG. 24illustrates a scanning pattern emitted through the bottom window 216 ofFIG. 1C, FIG. 25 illustrates a scanning pattern emitted through thebottom window 226 of FIG. 1E, and FIG. 26 illustrates a scanning patternemitted through the bottom window 5 of the present invention.

Compared to the bar code scanning patterns emitted through theconventional bottom windows 216 and 226, the scanning pattern emittedthrough the bottom window 5 of the present invention includes manyscanning lines heading in various directions. A total of 12 scanninglines are emitted from the bottom window 216 of FIG. 24, and a total of24 scanning lines are emitted from the bottom window 226 of FIG. 25. Byusing the scanning lines emitted through the bottom window 5 of thepresent invention, therefore, the bar code most probably can be scannedand can be read out very reliably.

Moreover, the bottom window 5 of the present invention is longer thanthe conventional bottom windows 216 and 226. Therefore, the bottomwindow 5 has a wider area on which the article will be passed to readthe bar code. This correspondingly enhances the efficiency of thereading operation.

FIG. 27 is a diagram illustrating a difference in the size of the areafor reading bar code between the conventional bar code reader and thebar code reader of the present invention. The readable areas shown inFIG. 27 are those where the bar code can be reliably read when the barcode erected, for example, in the vertical direction is turned by 360degrees on a horizontal plane.

In the case of the conventional bar code reader, the bottom window 5 hasa size of 6 inches×6 inches, which is short and, particularly, thereadable area in the direction of depth inevitably becomes narrow.Besides, the readable area is deviated toward the side window 4, and theoperator must pass the articles closer to the side window 4. Dependingupon the height of the operator, however, the article may not reach thisarea, and the reading operation is not efficient. With the bar codereader of the present invention, on the other hand, the bottom window 5has a size of 4 inches×7 inches, and the readable area in the directionof depth becomes broader toward the operator. Therefore, even a personhaving short arms is able to easily pass the articles within thereadable area.

When the article is passed on the bar code reader, the scanning beamemitted through the bottom window 5 is more likely to scan the articlewhen the bottom window 5 is deep. The reading ability, however, does notmuch change even when the bottom window 5 is not so wide or in thedirection in which the article is passed. Moreover, the sapphire glassis expensive and its price increases with an increase in the area.Therefore, the bottom window having a width of 6 inches isdisadvantageous from the standpoint of cost and this width is notnecessary, either.

On the other hand, the bottom window 5 of the present invention has awidth of 4 inches, which is necessary for maintaining the readingability and is further advantageous in suppressing the price of theglass.

FIG. 28. is a diagram illustrating the passage of a beam reflected bythe bar code in the bar code reader of the present invention startingfrom where the beam reflected by the bar code is incident on the polygonmirror 25. The reflected beam incident through the bottom window isreflected by the first mirror system and falls on the polygon mirror 25.The beam reflected by the bar code and by the reflection plane of thepolygon mirror 25 falls on the concave mirror 30. The beam reflected bythe polygon mirror 25 is further reflected and focused by the concavemirror 30 to fall on the first detector 28.

On the other hand, the beam incident through the side window isreflected by the second mirror system and falls on the polygon mirror25. The beam reflected by the bar code and is further downwardlyreflected by the reflection plane of the polygon mirror 25 and falls onthe Fresnel lens 32. The Fresnel lens 32 focuses the beam reflected bythe polygon mirror 25 so as to fall on the bottom mirror 33 whichreflects the beam reflected by the bar code toward the light-receivingsurface of the second detector 29.

FIG. 29 is a diagram illustrating a relationship of the length of theoptical passage of from the polygon mirror 25 to a position where thelaser beam can be best focused in the case when the bottom window 5 isshort. In FIG. 29, A-B-C-D represents a scanning beam emitted throughthe side window 4, and E-F-G-H represents a scanning beam emittedthrough the bottom window 5.

In the apparatus of FIG. 29, the optical passage A-B-C-D is longer thanthe optical passage E-F-G-H. This is because, the VLD module 21 isprovided under the side scanner portion 2.

When a lens and an aperture (details will be described later) forforming a beam are located close to the VLD module 21, the region forreading the bar code by the laser beam is determined depending upon adistance from the VLD module 21. Therefore, the position for mountingthe VLD module 21 in the bar code reader contributes to determining thesize of the bar code readable area.

In the case of FIG. 29, the distance from the VLD module 21 to aposition where the laser beam can be best focused is equal even in thecase of the position D or the position H. Depending upon the arrangementof the VLD module 21, which is a source of laser beam, however, thelengths of the two optical passages A-B-C-D and E-F-G-H change with thepolygon mirror 25 as a reference. The difference in the length betweenthe optical passages A-B-C-D and E-F-G-H is absorbed by a differencebetween the length of the optical passage A'-A of from the VLD module 21to the polygon mirror and the length of the optical passage A'-A"-E offrom the VLD module 21 to the polygon mirror through the mirror A'.

When the depth of the bottom window 5 is increased as indicated by abroken line, on the other hand, it is not allowed to mount the mirror Fon the same position as that of FIG. 29. That is, unless the mirror F ismoved to a position F' indicated by a broken line by the amount of anincrease in the length of the bottom window 5, the mirror F interceptsthe passage of the scanning beam and hinders the emission of thescanning beam. If the mirror F is moved to the position of the brokenline, therefore, the optical passage E-F-G-H becomes longer than theoptical passage A-B-C-D.

As a result, when the distance from the VLD module 21 to a positionwhere the laser beam can be best focused is set to be a position H ofthe bottom window 5, the position where the laser beam emitted throughthe side window 4 can be best focused becomes a position D' which isoutside the readable space. When the depth of the bottom window 5 islengthened as indicated by the broken line, therefore, it is notpossible to mount the VLD module 21 on the same position as that of FIG.29.

According to the present invention as shown in FIG. 30, therefore, theVLD module 21 is installed at an end of the bottom scanner portion 3most remote from the side scanner portion 2. With the VLD module 21being arranged in this way, the difference between optical passagelength A-B-C-D and the optical passage length E-F-G-H can be absorbed bythe difference between the optical passage length A'-A"-A and theoptical passage length A'-E.

The side scanner portion 2 is provided with the scanning mirror system,etc., and cannot provide a sufficiently wide space. It is thereforedifficult to lead the laser beam in the side scanner portion 2 tolengthen the optical passage of the beam emitted from the VLD module 21.According to the present invention shown in FIG. 30, the VLD module 21is installed at an end of the bottom scanner portion 3 most remote fromthe side scanner portion 2 of the bar code reader 1 to obtain space inwhich the laser beam can be lead about to adjust the length of theoptical passage.

According to the present invention, the laser beam supplied to the sidescanner portion 2 is caused to pass under the lower surface of thepolygon mirror 25 so as to intersect the axis of rotation of the polygonmirror 25. If the laser beam supplied to the side scanner portion 2 iscaused to pass over the polygon mirror 25, it becomes difficult toarrange the mirrors for guiding the laser beam to the scanning mirrorsystem in the side scanner portion 2. According to the presentinvention, however, the laser beam is passed under the polygon mirror 25to solve the above-mentioned problem.

FIG. 31 is a diagram illustrating an example of receiving the beamreflected by the bar code. In the case of FIG. 31, the scanning beamreflected by the polygon mirror 25 is incident on the pattern-generatingmirror 71 where it is downwardly reflected, and is further upwardlyreflected by the bottom mirror 72 so as to be emitted through the bottomwindow 5. In FIG. 31, the hatched area represents the area for readingbar codes of articles. The beam reflected by the bar code arrives at thepolygon mirror 25 passing through the same passage as the emitted beam,and is reflected toward the detector 73.

The beam reflected by the polygon mirror 25 is focused by the lens 74,downwardly reflected by the mirror 75 of which the reflection plane isfaced in a downwardly tilted direction, and arrives at the detector 73where it is received thereby.

In the case of this bar code reader 10, it is not possible to bring thelens 74 too close to the polygon mirror 25 due to the arrangement of themirror 71 and the bottom mirror 72. Accordingly, it is not possibledecrease the size of depth of the bar code reader 10. In this case, thedepth of not less than 450 mm is necessary.

In the case of a store having a wide area, the accounting counter mayhave a width of, for example, about 550 mm. In this case, the bar codereader 10 can be installed on the accounting counter without suppressingthe width of the bar code reader 10. In the case of a narrow store,however, the accounting counter may have a width of as narrow as from450 mm to 480 mm. In such a case, it becomes difficult to install thebar code reader 10 of FIG. 31 on the accounting counter.

FIG. 32 illustrates the arrangement of a light-receiving element in thebar code reader 1 according to the present invention. As describedalready, the first detector 28 according to the present invention isprovided on the bottom surface of the bar code reader 1. The beamreflected by the polygon mirror 25 is reflected by the concave mirror 30so as to be folded nearly into the center of the bar code reader 1.

In order that the scanning beam can be emitted through the bottom window5, the scanning beam reflected by the polygon mirror 25 is downwardlyreflected by the mirror ZBL1 mounted on the upper frame and is thenupwardly reflected by, for example, the concave mirror 30 and the mirrorZB2 provided on the VLD module 21. The hatched area shown in FIG. 32represents the area for reading bar codes of articles.

In order that the scanning beam is emitted through the bottom window 5as described above, there is arranged neither the mirror thatcorresponds to the bottom mirror 72 of FIG. 31 nor the optical systemthat contributes to generating the scanning beam on the bottom surfaceof the bar code reader 1. It is therefore possible to arrange the firstdetector 28 on the bottom surface of the bar code reader 1, and the beamreflected by the polygon mirror 25 is folded by the concave mirror 30toward the central portion of the bar code reader 1. Since the opticalsystem is thus arranged, the depth of the bar code reader 1 can bedecreased to be shorter than that of the bar code reader 10 explainedwith reference to FIG. 31 despite the depth of the bottom window 5 beingas long as 7 inches. In the case of the apparatus of FIG. 32, the depthcan be decreased to be not longer than 440 mm.

FIGS. 33A and 33B are a front view and a side view 5 of the concavemirror 30 used in the present invention. The through hole 31 is formednear the center of the concave mirror 30. Furthermore, on the back sideof the concave mirror 30 is provided a metallic mounting fitting 75 forbeing mounted on the lower frame 41 of the bar code reader 1. Themetallic mounting fitting 75 is folded in a U-shape and is made of aresilient member.

The focal point of the recessed mirror 30 must be brought to thebeam-receiving surface of the first detector 28. Due to mounting errors,however, the focal point of the concave mirror 30 often deviates fromthe light-receiving surface of the first detector 28. To avoid this, thepresent invention is provided with a mechanism capable of adjusting themounting angles of the concave mirror 30 in the horizontal direction andin the vertical direction.

FIG. 34 is a diagram illustrating the mechanism for adjusting the anglesof the concave mirror 30. Tapped holes 76 are formed near both ends of afolded portion 75' of the metallic mounting fitting 75, and a hole 77that serves as a fulcrum is formed near the central portion. On theother hand, the lower frame 41 of the bar code reader is provided with aprojection 78 and two elongated holes 79.

The hole 77 of the metallic mounting fitting 75 is fitted to theprojection 78 of the frame 41, and the concave mirror 30 is allowed toturn in the horizontal direction about the projection 78. Thepositioning of the concave mirror 30 in the horizontal direction isaccomplished by turning the concave mirror 30 about the projection 78 insuch a manner that the focal point of the concave mirror 30 ispositioned on the light-receiving surface of the first detector 28 asdescribed with reference to FIG. 32 and, then, the metallic mountingfitting 75 is secured to the lower frame 41 by using adjusting screws65.

The metallic mounting fitting 75 has resiliency. Therefore, the concavemirror 30 is turned back and forth with the folded portion 75" of themetallic mounting fitting 75 as a center to thereby adjust the mountingangle of the concave mirror 30. This adjustment is accomplished by usingan adjusting screw 66 provided in the lower frame 41. The adjustingscrew 66 is provided at a position opposed to the metallic mountingfitting 75 in a state where the concave mirror 30 is mounted on thelower frame 41. The end of the adjusting screw 66 abuts the back surfaceof the concave mirror 30 in a state where the concave mirror 30 ismounted on the lower frame 41. The angle of the concave mirror 30 in thevertical direction is adjusted by adjusting of the adjusting screw 66 tomove the concave mirror 30 back and forth.

Relying upon such a simply constructed mechanism, the beam reflected bythe concave mirror 30 can be brought to the light-receiving surface ofthe first detector 28 through a simple operation.

FIGS. 35A and 35B are a top view and a side view of the bottom mirror 33which causes the beam reflected by the bar code to be incident on thesecond detector 29 explained with reference to FIG. 28. A metallicmounting fitting 80 is attached to the bottom surface of the bottommirror 33. The bottom mirror 33 is mounted on the lower frame 41 throughthe metallic mounting fitting 80. The metallic mounting fitting 80, too,is made of a resilient member. The metallic mounting fitting 80 isfolded in a U-shape, and the inclination of the bottom mirror 33 and itsangle in the horizontal direction can be adjusted utilizing theresiliency of the metallic mounting fitting 80.

FIG. 36 is a diagram of when the bar code reader 1 of the presentinvention is viewed from the bottom side in a state where the cover isremoved. On the bottom surface of the bar code reader 1 are provided atotal of three screws for adjusting the angle of the concave mirror 30.As described with reference to FIG. 34, the adjusting screw 65 is usedfor adjusting the position of the concave mirror 30 in the horizontaldirection. The concave mirror 30 is turned and is so adjusted that thefocal point of the concave mirror 30 is located on the light-receivingsurface of the first detector 28 described with reference to FIG. 32.The concave mirror 30 is then secured to the lower frame 41 using theadjusting screws 65. The adjusting screw 66 is used for adjusting theposition of the concave mirror 30 in the vertical direction.

FIG. 36 further illustrates adjusting screws 63, 64 for adjusting thebottom mirror 33. The adjusting screw 63 is used for adjusting theinclination of the bottom mirror 33, and the end of the adjusting screw63 abuts the bottom surface of the bottom mirror 33. By adjusting of theadjusting screw 63, the inclination of the bottom mirror 33 is adjustedand the direction for reflecting the beam is adjusted.

The ends of the adjusting screws 64 are screwed, via elongated holes,into tapped holes formed near both ends of the metallic mounting fitting80. The tapped holes of the metallic mounting fitting 80 have a shapelike those of the metallic mounting fitting 75 for mounting the concavemirror 30. As in the case of the concave mirror 30, the metallicmounting fitting 80 is allowed to turn in the horizontal direction withthe fulcrum as a center. After the direction of the bottom mirror 33 isadjusted, the metallic mounting fitting 80 is secured to the lower frame41 using the adjusting screws 64.

FIGS. 37A and 37B are diagrams illustrating the bottom surface 81 inwhich is provided the bottom window 5 of the bar code reader 1 of thepresent invention. On the bottom surface 81 in which the bottom window 5is provided are formed protuberances 82 having a triangular shape incross section and extending in the direction of width of the bar codereader 1.

To read the bar code, the article is passed through the space above thebar code reader 1. Depending upon the operator, however, the article maybe moved in contact with the bottom surface 81. In such a case, when thebottom surface 81 in which the bottom window 5 is provided is flat, thearticle comes into contact with the bottom surface 1 over an increasedarea whereby the friction increases between the article and the bottomsurface 81, and it becomes not easy to move the article.

In order to cope with such a problem according to the bar code reader 1of the present invention, protuberances 82 are formed on the bottomsurface 81 in which the bottom window 5 is provided, and the contactarea is decreased between the article and the bottom surface 81 in orderto decrease frictional force between the article and the bottom surface81. The direction in which the protuberances 82 extend is in agreementwith the direction in which the article is passed to more effectivelydecrease the frictional force.

The protuberances 82 can be formed by resin molding together with thebottom surface 81. Moreover, a member forming protuberances may beadhered to the bottom surface.

The bar code reader 1 has a best-reading position 83 where the scanninglines are concentrated most and the reading probability becomes thehighest. In this bar code reader 1 as shown in FIG. 37B, the gaps amongthe protuberances 82 on the bottom surface 81 are changed enabling theoperator to recognize where the best-reading position is located.

That is, in this bar code reader 1, protuberances 82 are formedmaintaining a small gap on a portion corresponding to the best-readingposition 83. On the portions 84 deviated from the best-reading portion83, the gap among protuberances 82 is increased to be wider than the gapamong the protuberances at the best-reading position 83. Thus, bychanging the gaps among the protuberances 82 formed on the bottomsurface 81 in which the bottom window 5 is provided, the operatorvisually learns the best-reading position 83. Therefore, the operator isallowed to easily recognize where the best-reading position 83 islocated.

When a small article is to be passed, furthermore, the article may fallbetween the protuberances 82 causing the bar code reading to beimpaired. It is therefore desired that the gap among the protuberances82 is not so large. With the gaps among the protuberances 82 beingnarrow at the best-reading position, therefore, the article can bereliably passed at the best-reading position 83.

FIG. 38 illustrates a control unit 85 of the bar code reader 1. Thecontrol unit 85 of the bar code reader is provided with light detectorcircuits 101, 102 to which the first and second light detectors 28 and29 will be connected, a VLD control circuit 103 to which the VLD module21 will be connected, and a motor control circuit 104 to which thepolygon motor 20 will be connected. Operations of the units arecontrolled by these circuits. The control unit 85 further has connectorsfor connection to external units, such as a connector 105 for connectionto a power source cable for supplying electric power, a connector 106for an interface (I/F) cable for transferring the bar code data read bythe bar code reader 1 to a POS terminal, a connector 107 for connectionto a power source for supplying electric power to a scaling device, anda connector 108 to which can be connected a scanner of the hand-heldtype.

So far, as shown in FIG. 39, the control unit 85 had been verticallyinstalled on the back surface of the side scanner portion 2. In thiscase, however, the connectors 86 face downwards. When the cables 109need be connected to the connectors 86, therefore, the user had to tiltthe bar code reader 1 by lifting it up as shown in FIG. 39 so that he isallowed to make sure the kinds of the connectors to which the connectionis to be made.

However, the bar code reader 1 has been installed being buried in theaccounting counter, and it is very difficult to tilt the bar code reader1 by lifting it up. Therefore, the cables are difficult to connect.

FIG. 40 is a diagram explaining the connection of cables to the bar codereader 1 according to the present invention. In the bar code reader 1 ofthe present invention, the control unit 85 is horizontally arranged onthe bottom surface of the bar code reader 1, and the connectors 86 arefacing backwards. Therefore, the user is allowed to make sure the kindsof the connectors with the bar code reader 1 being horizontallyinstalled, and the connectors 109 can be efficiently connected.

FIG. 41 illustrates the back surface of the bar code reader 1 accordingto the present invention wherein a variety of connectors are arranged inthe horizontal direction. The bar code reader 1 is provided on the backsurface thereof with a power source cable connector 87 to which the DCpower source will be connected, an interface connector 88, and the likeconnectors.

FIG. 42 is a diagram illustrating the back surface of the bar codereader 1 in a state where the control unit 85 is mounted. The controlunit 85 has a variety of connectors 88 as explained with reference toFIG. 41.

FIG. 43 is a diagram illustrating the back surface of the bar codereader 1 in a state where the control unit 85 has been removed. From thebar code reader 1 are drawn a motor cable 111 connected to the polygonmotor 20, an ADS cable 112, an ADB cable 113, an ANA cable 114 and thelike cables, which are connected to the control unit 85.

FIG. 44A illustrates the constitution of the laser module 21. The lasermodule 21 comprises a semiconductor laser 91, a collimator lens 92 andan aperture 93. The laser beam emitted from the semiconductor laser 91diverges at a predetermined angle of divergence.

Therefore, the laser beam is focused through the collimator lens 92,passed through the aperture 93 to form a beam which is then emitted tothe bar code readable area.

Here, as shown in FIG. 45, the laser beam emitted from the semiconductorlaser 91 is differently diverged depending upon the vertical directionand the horizontal direction. The beam is diverged at an angle of fromabout 5° to about 11° in the horizontal direction and is diverged at anangle of from about 24° to about 37° in the vertical direction. Besides,greatly different characteristics are exhibited depending upon theindividual semiconductor lasers 91, and the angle of divergence differsgreatly depending upon the individual semiconductor lasers 91.

Here, the shape of the laser beam that is emitted is defined by thediameter of the aperture 93; i.e., the beam diameter is shaped by theaperture 93. FIG. 44B illustrates a relationship between the distancefrom the aperture and the beam diameter of when there is employed alaser beam that is emitted after being shaped by the aperture. When itis presumed that an optimum beam diameter that is suited for reading thebar code is 550 μm, the bar code readable area becomes as shown in, forexample, FIG. 44B. When the beam diameter is too great, it becomesdifficult to read the bar code having narrow gaps among the bars and,particularly, having a narrow bar width, causing the bar code readingefficiency to decrease. It is therefore desired that the beam diameteris as small as possible on the readable area.

Described below with reference to FIGS. 46A and 46B is the problem thatarises from a difference in the angle of divergence of the laser beamemitted from the semiconductor laser 91 depending upon the verticaldirection and the horizontal direction. Even when an optical beamdiameter is obtained in the horizontal direction in which the angle ofdivergence of the beam is small as shown in FIG. 46A, the angle ofdivergence becomes large in the vertical direction that is shown in FIG.46B and, hence, the beam of a large diameter falls on the aperture 93.From the standpoint of shaping the beam, the aperture 93 has the samediameter in both the vertical and horizontal directions. In the verticaldirection, therefore, the laser beam is partly intercepted by theaperture 93, and the loss of laser beam energy increases and theefficiency for utilizing the beam decreases. In the worst case, the beamis utilized at an efficiency of about 18%.

The efficiency for utilizing the beam can be enhanced by increasing thediameter of the aperture 93, decreasing the f-value of the collimatorlens 92 (shortening the focal distance), or by increasing the distancebetween the semiconductor laser 91 and the collimator lens 92. FIG. 47illustrates a relationship between the distance from the aperture 93 andthe beam diameter of when the above-mentioned countermeasure is takenfor the laser beam.

In FIG. 47, a curve ADN represents characteristics of when the diameterof the aperture 93 is the same as the conventional one (characteristicsADN are the same as the characteristics shown in FIG. 44B), a curve ADLrepresents characteristics of when the diameter of the aperture 93 isincreased, a curve LFS represents characteristics of when the f-value ofthe collimator lens 92 is decreased or when the distance is increasedbetween the semiconductor laser 91 and the collimator lens 92.

When the diameter of the aperture 93 is increased, the laser beam isless intercepted in the vertical direction, and the efficiency forutilizing the beam increases. However, since the aperture 93 has a largediameter, it becomes difficult to squeeze the beam. In this case asrepresented by the curve ADL in FIG. 47, therefore, the readable area inwhich the beam diameter is 550 μm becomes narrower than an area of thecurve ADN of when the aperture 93 has an ordinary diameter. As a result,the position where the beam can be most squeezed becomes more remotethan that of when the aperture 93 has an ordinary diameter. In thehorizontal direction, the laser beam almost completely passes throughthe aperture 93 as the diameter of the aperture 93 increases, and thelaser beam is no longer substantially shaped.

When the f-value of the collimator lens 92 is decreased, the beamdiameter can be most squeezed at a position closer than that of when alens having a large f-value is used as represented by a curve LFS inFIG. 47. In this case as shown in FIG. 48A, ideal beam shape and idealefficiency for utilizing the beam can be accomplished in the verticaldirection in which the beam diverges at an increased angle, and there isno particular problem concerning the efficiency for utilizing the beam.In the horizontal direction in which the beam diverges at a small angle,however, the beam is almost not intercepted by the aperture 93 as shownin FIG. 48B and the beam is not shaped, giving rise to the occurrence ofa problem in that the beam shape is lost. In the horizontal direction,therefore, the beam forms an image in space in front of the readingspace, and the readable area becomes narrow since the image-formingposition differs depending upon the vertical direction and the lateraldirection.

Even when the distance is increased between the semiconductor laser 91and the collimator lens 92, the same problem occurs as when thecollimator lens 92 having a small f-value is employed.

To read the bar code as described above, it becomes necessary to enhancethe efficiency for utilizing the laser beam and to broaden as much aspossible the readable area for reading the bar code in an optimum way.

The laser module 21 used in the present invention solves theabove-mentioned problem and expands the margin of light quantity yetmaintains a beam diameter for accomplishing a predetermined resolutionfor reading the bar code. The laser module 21 of the present inventionhas a beam diameter which is the same in both the vertical direction andthe horizontal direction, so that beam is hardly intercepted by theaperture and so that a range in which an optimum beam diameter ismaintained is expanded.

FIGS. 49A and 49B are diagrams explaining a problem that arises when useis made of a collimator lens 92 having a relatively large f-value andexplaining a method of solution. In the case of the laser module 21 ofFIGS. 49A and 49B, no problem arises concerning the shape of the beam inthe lateral direction in which the beam diverges at a small angle, andthe beam intercepted by the aperture 93 can still be utilizedmaintaining an ideal efficiency. In the vertical direction in which thebeam diverges at a large angle, however, the beam is much intercepted bythe aperture and the efficiency for utilizing the beam decreases thoughthere is no problem concerning the shape of the beam.

This problem can be solved if the beam diameter in the verticaldirection is decreased without decreasing the quantity of beam, so as tobecome nearly equal to the beam diameter in the horizontal direction.

FIGS. 50A and 50B are diagrams illustrating the principle of means forthis solution. FIG. 50A illustrates a rectangular prism 94. When a laserbeam is incident upon the rectangular prism 94 at a predetermined angle,the laser beam is refracted by the rectangular prism 94.

Here, the ratio of the laser beam emitted from the semiconductor laser91 in the vertical direction to the laser beam emitted from thesemiconductor laser 91 in the horizontal direction is equal to the ratioof their angles of divergence. When a particular value within theabove-mentioned range of angles of divergence is used, the ratio of theangle of divergence in the vertical direction to the angle of divergencein the horizontal direction, i.e., the ratio of the beam diameters is2.7 to 1. Here, therefore, the beam diameter in the vertical directionmust be contracted at a ratio of 2.7 to 1. When the beam is refracted bythe rectangular prism 94, the diameter of the beam emitted from therectangular prism 94 is changed depending upon the angle of refraction.FIG. 50A illustrates an example where the beam diameter is contracted atthe above-mentioned ratio of 2.7 to 1.

The wavelength of the laser beam emitted from the semiconductor laseris, for example, 670 nm. When a glass constituting the rectangular prism94 has a refractive index n of 1.5134 and the rectangular prism 94 hasan inner angle θ of 37.8280°, the laser beam incident on a plane 94a ofthe rectangular prism 94 at right angles goes out at angle of 68.15°with respect to a perpendicular 94p to the oblique line 94b of therectangular prism 94. Here, the Y-direction corresponds to the verticaldirection of the laser beam. When the laser beam from the collimatorlens 92 is incident perpendicularly upon the plane 94a of therectangular prism 94, the ratio of the diameter of the beam incident onthe rectangular prism 94 to the diameter of the laser beam going outfrom the rectangular prism 94 can be set to be 2.7 to 1 as shown in FIG.50B.

The rectangular prism 94 does not work in the horizontal direction andthe beam diameter does not change; i.e., the diameter of the beamemitted from the semiconductor laser 91 is maintained.

FIG. 51A is a sectional view of the laser beam at a position IN in FIG.50B. Referring to FIG. 50B, when the laser beam has a diameter a in thevertical direction and a diameter b in the horizontal direction at theposition IN (a:b=2.7:1), the beam diameter in the vertical direction iscontracted to 1/2.7 through the rectangular prism 94. At a position OUT,therefore, the laser beam has a diameter b in the vertical direction.Accordingly, the laser beam at the position OUT has a circular shape incross section as shown in FIG. 51B.

FIG. 52 is a diagram illustrating the arrangement of the semiconductorlaser 91, collimator lens 92, aperture 93 and rectangular prism 94.Thus, the beam diameter is contracted in the vertical direction by usingthe rectangular prism 94, and is set to be the same (or nearly the same)as the beam diameter in the horizontal direction, so that the laser beamis hardly intercepted by the aperture 93 thereby to enhance theefficiency of using the light.

FIGS. 53A and 53B illustrate the constitution for solving the probleminherent in the VLD module 21 which uses a collimator lens (f=3.6 mm)having a small f-value explained with reference to FIGS. 48A and 48B.

In the case of the VLD module 21 explained with reference to FIGS. 48Aand 48B, no problem arises in the vertical direction but a problemarises in the horizontal direction in that the aperture 93 almost doesnot act and the beam is not shaped. In the case of FIGS. 53A and 53B,therefore, the beam diameter is expanded in the lateral direction.

When the beam diameter is expanded at a ratio of 1 to 2.7, therectangular prism 94 which is used may be the same as the one explainedwith reference to FIGS. 50A and 50B. The difference from FIGS. 50A and50B is with respect to the arrangement of the rectangular prism 94. Inthe case of FIGS. 53A and 53B, the laser beam is incident at an angle of68.15° with respect to a perpendicular 94p to the oblique line 94b ofthe rectangular prism 94. Here, the direction of plane corresponds tothe horizontal direction of the laser beam. This enables the beamdiameter to be expended to 2.7 times as great in the horizontaldirection.

FIG. 54A is a diagram illustrating in cross section the laser beam atthe position IN of FIG. 53B. Referring to FIG. 53B, when the laser beamhas a diameter a in the vertical direction and a beam diameter b in thehorizontal direction at the position IN (a:b=1:2.7), the beam diameterin the vertical direction is expanded to 2.7 times as great through therectangular prism 94. Therefore, the diameter of the laser beam in thevertical direction becomes b at the position OUT. As shown in FIG. 54B,therefore, the laser beam at the position OUT has a circular shape incross section.

FIG. 55 is a diagram illustrating a state where there are arranged therectangular prism 94, semiconductor laser 91, collimator lens 92 andaperture 93 of FIGS. 53A and 53B. By using the rectangular prism 94 asshown in FIG. 55, the beam diameter can be expanded in the horizontaldirection so that the beam incident on the aperture 93 will have thesame diameter in the horizontal direction and in the vertical direction.

Here, various problems arise in that the laser beam emitted from therectangular prism 94 and arriving at the aperture 93 becomes too greator too small depending upon the tolerance of angle of the rectangularprism 94 and the positional relationship with respect to the VLD module21.

FIG. 56A is a diagram explaining this problem. When, for example, thebeam incident on the rectangular prism 94 is not a parallel beam, theposition where the laser beam is focused is determined depending uponthe distance between the semiconductor laser 91 and the collimator lens92, and the initial focal position f1 may extend as represented by afocal position f2.

This problem can be solved by turning, as shown in FIG. 56B, thecollimator lens 92 with the optical axis thereof as a center in adirection in which the beam is changed by the rectangular prism 94. Thatis, by turning the collimator lens 92, the diameter of the beam arrivingat the rectangular prism 94 can be decreased depending upon theinclination of the collimator lens 92.

Therefore, even when the rectangular prism 94 is secured to the VLDmodule 21 by such means as adhesion and cannot be adjusted, expansion inthe diameter of the laser beam arriving at the aperture 93 can becanceled by contracting the diameter of the laser beam arriving at therectangular prism 94 by adjusting the angle of the collimator lens 92.

This method can be applied even when the initial focal distance tends tobe shortened. That is, contraction in the diameter of the laser beamarriving at the aperture 93 can be canceled by expanding the diameter ofthe laser beam arriving at the rectangular prism 94 by adjusting theangle of the collimator lens 92.

The foregoing description has employed the rectangular prism 94. This isbecause the rectangular prism 94 makes it possible to minimize thevertical angle of the prism and, hence, to decrease the size of the VLDmodule 21 as a whole. In particular, when there is no need to decreasethe size of the VLD module 21, it is allowable to use a prism 95 whichis not right angled as shown in FIG. 57. In the case of the prism 95 ofFIG. 57, the angles a and b are different.

FIGS. 58A to 58C illustrate examples of changing the beam diameter byusing means other than the prism. Here, cylindrical lenses 96a, 96b areused. The cylindrical lens exhibits the focusing action concerning oneaxis only between the two axes intersecting at right angles and can,hence, be adapted for contracting or expanding the diameter of the laserbeam in either the vertical direction or the horizontal direction.

FIG. 58A is a diagram illustrating means for contracting the beamdiameter in the vertical direction. In FIG. 58A, a cylindrical convexlens 96a and a cylindrical concave lens 96b are used in combination. Thelenses are arranged in the order of collimator lens 92, cylindricalconvex lens 96a and cylindrical concave lens 96b starting from the sidecloser to the semiconductor laser 91.

When the cylindrical convex lens 96a only is arranged adjacent thecollimator lens 92, the laser beam squeezed by the collimator lens 92 isfurther squeezed in the vertical direction only through the cylindricalconvex lens 96a. The laser beam is squeezed in the horizontal directionby the collimator lens 92 only but is squeezed in the vertical directionby both the collimator lens 92 and the cylindrical convex lens 96a.Compared to the beam of the horizontal direction which does not receivethe action of the cylindrical convex lens 96a, therefore, the laser beamemitted in the vertical direction forms an image at a short distance. Inthis state, the beam diameter incident on the aperture 93 becomessmaller than that of the beam in the horizontal direction, giving riseto the occurrence of a problem in that the beam emitted to the readablearea loses its shape.

As a means for correcting the shape of the beam, the cylindrical concavelens 96b is provided in a subsequent stage of the cylindrical convexlens 96a. The cylindrical concave lens 96b decreases the degree ofsqueeze of the cylindrical convex lens 96a. In FIG. 58A, the beam in thehorizontal direction is indicated by broken lines. Due to the actions ofthe cylindrical convex lens 96a and cylindrical concave lens 96b asshown in FIG. 58A, the beam incident on the aperture 93 has nearly thesame diameter in both the horizontal direction and the verticaldirection.

FIG. 58B is a diagram illustrating means for expanding the beam diameterin the vertical direction. In the case of FIG. 58B, the laser beamemitted from the semiconductor laser 91 passes through the collimatorlens 92, cylindrical concave lens 96b and cylindrical convex lens 96a inthe order mentioned, and is incident upon the aperture 93. In FIG. 58,the solid lines represent the beam in the horizontal direction anddotted lines represent the beam in the vertical direction.

The beam of the horizontal direction squeezed by the collimator lens 92is expanded into a predetermined magnification through the cylindricalconcave lens 96b. On the other hand, the beam in the vertical directiondoes not receive the action of the cylindrical concave lens 96b and canbe more squeezed than the beam in the horizontal direction.

Here, the beam in the horizontal direction is expanded by thecylindrical concave lens 96b but the beam in the vertical direction doesnot receive the action of the cylindrical concave lens 96b. Therefore,the beam in the horizontal direction forms an image at a position at anincreased distance. When the cylindrical concave lens 96b only isdisposed in the subsequent stage of the collimator lens 92, therefore,the beam of the horizontal direction emitted to the readable area maylose its shape.

To cope with this in the case of FIG. 58B, the cylindrical convex lens96a is inserted in the subsequent stage of the cylindrical concave lens96b to correct the beam. By suppressing the degree of expansion of thebeam in the horizontal direction or by focusing the beam in thehorizontal direction through the cylindrical convex lens 96a, the degreeof converging the beam can be set to be nearly the same in both thehorizontal direction and the vertical direction.

In FIGS. 58A and 58B, use is made of two concave and convex cylindricallenses 96a and 96b. As shown in FIG. 58C, however, it is also possibleto use a cylindrical double-sided lens 96c like the one obtained bysticking two concave and convex cylindrical lenses 96a and 96b together.In this case, however, the distance becomes zero between the two lenses96a and 96b, and the beam is converted within the same medium. Ittherefore becomes necessary to form a lens surface having a radius ofcurvature which is smaller when the two cylindrical lenses 96a and 96bare used.

FIG. 59 illustrates a means in which the laser beam emitted from the VLDmodule 21 is split to generate dissimilar scanning beams A and B.

The laser beam emitted from the VLD module 21 is split into two beams Aand B through a beam-splitting means (half-mirror in the aforementionedembodiment) 22. The two beams A and B are reflected by a smallreflection mirror 30' provided at the center of the concave mirror 30toward the polygon mirror 25. The laser beams reflected by the polygonmirror 25 are reflected by the first mirror system 26 and are emittedthrough the bottom window 5, one beam serving as a scanning beam A andthe other beam serving as a scanning beam B.

The beams reflected by the bar code 8 are further reflected by thepolygon mirror 25 to fall on the concave mirror 30. The reflected beamcorresponding to the scanning beam A falls on the first light detector28 being reflected by the concave mirror 30, and the reflected beamcorresponding to the scanning beam B falls on the second light detector29 being reflected by the concave mirror 30.

FIGS. 60A and 60B illustrate examples of beam-splitting means. In FIG.60A, the laser beam emitted from the VLD module 21 is split into a beamA and a beam B by a half-mirror 22. In FIG. 60B, the laser beam emittedfrom the VLD module 21 is split into a beam A and a beam B by ahalf-cube (or PBS) 22'.

FIGS. 61A and 61B are diagrams of the VLD module 21 of the presentinvention incorporating these prism, splitting means, collimator lens,etc. In FIGS. 61A and 61B, reference numeral 91 denotes a semiconductorlaser, and 92 denotes a collimator lens. The collimator lens 92 iscontained in a block 97 made of, for example, aluminum. The block 97 canbe adjusted for its position in the right-and-left direction, and theposition of focal point of the laser beam is adjusted by the block 97.The block 97 is urged from the upper direction by a resilient urgingplate 98, so that its position is secured.

Reference numeral 94 denotes a rectangular prism, and a laser beamemitted from the semiconductor laser 91 is incident on the rectangularprism 94 through the oblique line 94b of the rectangular prism 94. Thelaser beam refracted by the rectangular prism 94 is shaped through theaperture 93 and is split into a beam A and a beam B by the half-mirror22.

As shown in FIG. 3, the beam A is projected onto the polygon mirror 25through the hole 31 formed in the concave mirror 30. On the other hand,the beam B is projected onto the reflection mirror 23.

FIG. 62A is a diagram viewing the block 97 containing the collimatorlens 92 from the upper side, and FIG. 62B is a diagram viewing the block97 containing the collimator lens 92 from the front side.

The collimator lens 92 is mounted on the block 97 being inclined by apredetermined angle with respect to the optical axis of the laser beam.The semiconductor laser 91 exhibits different angles of divergencedepending upon the vertical direction and the horizontal direction, andfurther exhibits astigmatism. This is a phenomenon in which the positionfor emitting the beam in the horizontal direction and the position foremitting the beam in the vertical direction are deviated from eachother, arousing a problem in that the focal position of the laser beamis deviated.

In order to solve the problem of astigmatism or the problem of FIGS. 56Aand 56B, the collimator lens 92 according to the present invention ismounted being tilted by a predetermined angle with respect to theoptical axis. The angle for mounting the collimator lens 92 may bedetermined in advance depending upon a variety of conditions. Thougheach semiconductor laser 91 has its own characteristics, the angle formounting the collimator lens 92 is hardly dependent upon the differencein the characteristics of the semiconductor laser 91. The effects can beexhibited to a considerable degree if an average angle is employed tocope with the semiconductor laser 91.

What is claimed is:
 1. A bar code reader comprising:a first readingwindow; a second reading window disposed next to said first readingwindow and at a predetermined inclination angle with respect thereto;said bar code reader further comprising, in a co-planar arrangement withrespect to a specified plane:a source of light for emitting an initialray of light; splitting means for splitting the initial ray of lightinto a first ray of light following a first optical path from the sourceof light and a second ray of light following a second optical path fromthe source of light; rotary scanning means having a plurality ofreflection planes in rotation about an axis of rotation included in thespecified plane, said rotary scanning means having the first and secondrays of light incident thereupon from different respective directionsand reflecting the first and second rays of light therefrom to formfirst and second scanning beams respectively following the first andsecond optical paths; a first mirror system that reflects the firstscanning beam through said first reading window to impinge on a barcode, a first reflected scanning beam being reflected therefrom tofollow the first optical path back toward the source of light; a secondmirror system that reflects the second scanning beam through said secondreading window to intersect with the first scanning beam and impinge onthe bar code, a second reflected scanning beam being reflected therefromto follow the second optical path back toward the source of light; firstand second reflecting means for guiding the second ray of light to saidrotary scanning means; first focusing means for focusing the firstreflected scanning beam toward a first detector; and second focusingmeans for focusing the second reflected scanning beam toward a seconddetector.
 2. A bar code reader according to claim 1, wherein the firstdetector and the second detector are disposed in the specified plane. 3.A bar code reader according to claim 1, wherein said first detector andsaid second detector are disposed at respective positions deviated fromthe specified plane.
 4. A bar code reader according to claim 1,wherein:said first reflecting means and said second reflecting means aredisposed at respective positions in the specified plane and oriented tobe opposed to each other; said rotary scanning means is disposed betweensaid first and second reflecting means; said first reflecting meansreflects the second ray of light from said splitting means toward saidsecond reflector means to pass through the axis of rotation of saidrotary scanning means; and said second reflecting means reflects thesecond ray of light toward said rotary scanning means.
 5. A bar codereader according to claim 4, wherein the second ray of light passesthrough the axis of rotation of said rotary scanning means at a positionunder said rotary scanning means.
 6. A bar code reader according toclaim 1, wherein:said first focusing means comprises a concave mirrordisposed between said source of light and said rotary scanning means onan optical axis of the initial ray of light; the first scanning beam andthe first reflected scanning beam are incident upon one of the pluralityof reflection planes facing the first detector; and the concave mirrordefines an aperture therethrough and through which the initial ray oflight passes.
 7. A bar code reader according to claim 6, wherein:thefirst detector is disposed adjacent to a bottom surface of said bar codereader; and a light-receiving surface of the first detector faces areflective surface of the concave mirror.
 8. A bar code reader accordingto claim 1, wherein said second focusing means comprises a lens disposedbetween said rotary scanning means and the second detector, the lensfocusing the second reflected scanning beam onto a light-receivingsurface of the second detector.
 9. A bar code reader according to claim8, wherein the second detector is disposed with the light-receivingsurface thereof facing the bottom surface of said bar code reader, andfurther comprising a reflection mirror, disposed between the lens andthe second detector, that reflects the second reflected scanning beamfrom the lens toward the second detector.
 10. A bar code readeraccording to claim 1, wherein:the first scanning beam passes through afirst converged position at which the first scanning beam attains aminimum diameter thereof; the second scanning beam passes through asecond converged position at which the second scanning beam attains aminimum diameter thereof; and said source of light is disposed at aposition for which a distance from the first converged position to thereflection plane upon which the first scanning beam is incident to belarger than a distance from the second converged position to areflection plane of said rotary scanning means upon which the secondscanning beam is incident.
 11. A bar code reader according to claim 1,wherein said first reading window comprises a transparent plate having amajor axis parallel to the specified plane and a minor axisperpendicular to the specified plane.
 12. A bar code reader according toclaim 11, wherein the minor axis is 7 inches long and the minor axis is4 inches long.
 13. A bar code reader according to claim 1, furthercomprising:a side scanner portion including said second reading windowand a mirror frame; a bottom scanner portion including said firstreading window, an upper frame having a plurality of upper sidesurfaces, and a lower frame disposed below and adjacent to said upperframe and having a plurality of lower side surfaces; a plurality offirst reflection mirrors disposed on the upper side surfaces anddownwardly tilted to downwardly reflect the first scanning beam incidentfrom said rotary scanning means; a plurality of second reflectionmirrors disposed on the lower side surfaces and oriented to reflect thefirst scanning beam incident from said plurality of first reflectionmirrors toward said first reading window; a plurality of thirdreflection mirrors disposed on said lower side surfaces and upwardlytilted to upwardly reflect the second scanning beam incident from saidrotary scanning means; and a plurality of fourth reflection mirrorspositioned in the mirror frame and of which the reflection planes arefaced toward downwardly tilted to reflect the second scanning beam,incident from said third plurality reflection mirrors, in a horizontaldirection through said second reading window.
 14. A bar code readeraccording to claim 1, wherein said bottom scanner portion furtherincludes an upper surface having said first reading window set thereinand defining a plurality of protuberances therefrom for decreasingfriction between the upper surface and an article that passes in contactwith the upper surface.
 15. A bar code reader according to claim 14,wherein the protuberances are linearly extended in a direction in whichthe article passes.
 16. A bar code reader according to claim 15, whereineach of the protuberances has a tapered cross section.
 17. A bar codereader according to claim 15, wherein said protuberances are arranged ina first group, with a first gap between respective ones thereof, and asecond group, with a second gap between respective ones thereof, thefirst gap being less than the second gap and the first group indicatinga portion of the upper surface where the bar codes can be best read out.18. A bar code reader according to claim 1, wherein a control unit isinstalled on the bottom surface of said reader, said control unit havinga first connector for supplying electric power to members constitutingsaid reader and a second connector for inputting and outputting signals,the first and second connectors being disposed near the bottom surfaceat a rear portion thereof and directed horizontally.
 19. A bar codereader according to claim 1, wherein said source of light includes:asemiconductor laser; a third focusing means for focusing a laser beamemitted from the semiconductor laser and; a beam shaping means forchanging a diameter of the laser beam in a specified axis of aright-angle cross section of the laser beam.
 20. A bar code readeraccording to claim 19, wherein said splitting means is incorporated insaid source of light.
 21. A bar code reader according to claim 19,wherein:said beam shaping means comprises a prism having a verticalangle corresponding to an amount by which said beam shaping meanschanges the diameter of the laser beam; and the diameter of the laserbeam in the specified axis is changed by refracting the laser beam in apredetermined direction.
 22. A bar code reader according to claim 19,wherein said beam shaping means comprises a cylindrical lens.
 23. A barcode reader according to claim 22, wherein the cylindrical lens includesa concave cylindrical lens and a convex cylindrical lens.
 24. A bar codereader according to claim 22, wherein the cylindrical lens is adouble-sided cylindrical lens having a concave surface on a first sidethereof and a convex surface on a second side thereof.
 25. A bar codereader according to claim 19, wherein said focusing means is disposed atan adjustable angle with respect to an optical axis of the laser beam.26. A bar code reader according to claim 19, wherein the third focusingmeans is mounted in a block having a position movable along the opticalaxis of the laser beam and is tilted with respect to the optical axis ofthe laser beam.
 27. A bar code reader according to claim 21, wherein theprism has a right triangular base.
 28. A bar code reader, comprising:afirst reading window transmitting therethrough a first scanning beamobtained from a first ray of light and attaining a minimum diameterthereof at a first position; a second reading window disposed next tosaid first reading window and at a predetermined inclination angle withrespect thereto, said second reading window transmitting therethrough asecond scanning beam to intersect the first scanning beam, the secondscanning beam being obtained from a second ray of light and attaining aminimum diameter thereof at a second position; and a rotary scanningunit having a plurality of reflection planes rotating about an axis ofrotation intersected by the second ray of light,a first reflection planeof said rotary scanning unit reflecting the first ray of light therefromas the first scanning beams, a second reflection plane of said rotaryscanning unit reflecting the second ray of light therefrom as the secondscanning beam, a length of a first optical path traversed by the firstray of light from a point of origination thereof to the first positionbeing equal to a length of a second optical path traversed by the secondray of light from a point of origination thereof to the second position,and a distance from the first reflection plane to the first positionbeing larger than a distance from the second reflection plane to thesecond position, and the axis of rotation of said rotary scanning unitforming a common plane with the first ray of light and the second ray oflight.
 29. A bar code reader according to claim 28, further comprising:asource of light emitting an initial ray of light; and a beam splittersplitting the initial ray of light into the first and second rays oflight.
 30. A bar code reader, comprising:a beam splitter splitting anincident laser beam into a first beam attaining a minimum diameterthereof at a first position and a second beam attaining a minimumdiameter thereof at a second position, a length of a first optical pathtraversed by the first beam from said beam splitter to the firstposition being equal to a length of a second optical path traversed bythe second beam from said beam splitter to the second position; and arotating mirror having first and second reflective faces in rotationabout an axis of rotation and directed in different respectivedirections,the first beam being reflected from the first reflective faceas the first scanning beam, the second beam intersecting the axis ofrotation of said rotating mirror and being reflected from the secondreflective face as the second scanning beam, and a distance from thefirst face to the first position being greater than a distance from thesecond face to the second position , and the axis of rotation of saidrotating mirror forming a common plane with the first beam and thesecond beam.
 31. A bar code reader, comprising:a source of light thatemits an initial ray of light; a beam splitter that splits the initialray of light into at least a first ray and a second ray; a polygonmirror arranged in a common plane with said source of light and saidbeam splitter and having an axis of rotation included in the commonplane, said polygon mirror rotating about the axis of rotation to scanlight rays incident thereto; and a plurality of mirrors arranged in thecommon plane and reflecting to said polygon mirror at least one of thefirst ray and the second ray.
 32. A bar code reader according to claim31 further comprising:light receiving means arranged in the common planeand receiving a light ray reflected from a bar code presented to saidbar code reader; and light focusing means arranged in the common planeand focusing into said light receiving means the light ray reflected bythe bar code.